Atomic structure and periodic table · Web viewWrite the word equation Potassium m anganate(VII) +...

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A. ATOMIC STRUCTURE

The atom is the smallest particle of an element that take part in a chemical reaction.The atom is made up of three subatomic particle:

(i)Protons(ii)Electrons(iii)Neutrons

(i)Protons1.The proton is positively charged2.Is found in the centre of an atom called nucleus3.It has a relative mass 14.The number of protons in a atom of an element is its Atomic number

(ii)Electrons 1.The Electrons is negatively charged2.Is found in fixed regions surrounding the centre of an atom called energy levels/orbitals.3.It has a relative mass 1/1840

4.The number of protons and electrons in a atom of an element is always equal

(iii)Neutrons1.The Neutron is neither positively or negatively charged thus neutral.2.Like protons it is found in the centre of an atom called nucleus 3.It has a relative mass 14.The number of protons and neutrons in a atom of an element is its Mass number

Diagram showing the relative positions of protons ,electrons and neutrons in an atom of an element

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Diagram showing the relative positions of protons, electrons and neutrons in an atom of Carbon

The table below show atomic structure of the 1st twenty elements.

Element Symbol Protons Electrons Neutrons Atomic

numberMass number

Hydrogen H 1 1 0 1 1Helium He 2 2 2 2 4Lithium Li 3 3 4 3 7Beryllium Be 4 4 5 4 9Boron B 5 5 6 5 11Carbon C 6 6 6 6 12Nitrogen N 7 7 7 7 14Oxygen O 8 8 8 8 16Fluorine F 9 9 10 9 19Neon Ne 10 10 10 10 20Sodium Na 11 11 12 11 23Magnesium Mg 12 12 12 12 24Aluminium Al 13 13 14 13 27Silicon Si 14 14 14 14 28Phosphorus P 15 15 16 15 31Sulphur S 16 16 16 16 32Chlorine Cl 17 17 18 17 35Argon Ar 18 18 22 18 40Potassium K 19 19 20 19 39Calcium Ca 20 20 20 20 40

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Most atoms of elements exist as isotopes. Isotopes are atoms of the same element, having the same number of protons/atomic number but different number of neutrons/mass number.By convention, isotopes are written with the mass number as superscript and the atomic number as subscript to the left of the chemical symbol of the element. i.e.

mass number atomic number m n X symbol of element

Below is the conventional method of writing the 1st twenty elements showing the mass numbers and atomic numbers;1

1H 42He 7

3Li 94Be 11

5B 126C

147N 16

8O 199F 20

10Ne 2311Na 24

12Mg27

13Al 2814Si 31

15P 3216S 35

17Cl 4018Ar

3919K 40

20C

The table below shows some common natural isotopes of some elements

Element Isotopes Protons Electrons Neutrons Atomic number

Massnumber

Hydrogen 11H

21H(deuterium)

31H(Tritium)

111

111

023

111

123

Chlorine 3517Cl

3717Cl

1717

1717

1820

1717

3537

Potassium

3919K

4019K

4119K

191919

191919

202122

191919

394041

Oxygen 168O

188O

88

88

810

88

1618

Uranium 23592U

23892U

9292

9292

143146

9292

235238

Neon 2210Ne

2010Ne

2110Ne

101010

101010

121011

101010

222021

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The mass of an average atom is very small (10-22 g).Masses of atoms are therefore expressed in relation to a chosen element. The atom recommended is 12C isotope whose mass is arbitrarily assigned as 12.000 atomic mass units(a.m.u) .All other atoms are compared to the mass of 12C isotope to give the relative at The relative atomic mass(RAM) is therefore defined as “the mass of average atom of an element compared to 1/12 an atom of 12C isotope whose mass is arbitrarily fixed as 12.000 atomic mass units(a.m.u) ” i.e;

RAM = mass of atom of an element1/12 of one atom of 12C isotope

Accurate relative atomic masses (RAM) are got from the mass spectrometer. Mass spectrometer determines the isotopes of the element and their relative abundance/availability. Using the relative abundances/availability of the isotopes, the relative atomic mass (RAM) can be determined /calculated as in the below examples.

a) Chlorine occurs as 75% 3517Cl and 25% 37

17Cl isotopes. Calculate the relative atomic mass of Chlorine.

Working100 atoms of chlorine contains 75 atoms of 35

17Cl isotopes100 atoms of chlorine contains 75 atoms of 37

17Cl isotopesTherefore;RAM of chlorine = ( 75/100 x 35) + 25/100 x 37 = 35.5 Note that:Relative atomic mass has no unitsMore atoms of chlorine exist as 35

17Cl(75%) than as 3717Cl(25%)

therefore RAM is nearer to the more abundant isotope.

b) Calculate the relative atomic mass of potassium given that it exist as;93.1% 39

19K , 0.01% 4019K , 6.89% 41

19K ,

Working100 atoms of potassium contains 93.1 atoms of 39

19K isotopes100 atoms of potassium contains 0.01 atoms of 40

19K isotopes100 atoms of potassium contains 6.89 atoms of 41

19K isotopesTherefore;RAM of potassium = (93.1/100 x39) + (0.01/100 x 40) +(6.89 /100 x 39)

= Note that:Relative atomic mass has no units

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More atoms of potassium exist as 3919K (93.1%) therefore RAM is

nearer to the more abundant 3919K isotope.

c) Calculate the relative atomic mass of Neon given that it exist as;90.92% 20

10Ne , 0.26% 2110Ne , 8.82% 22

10Ne,

Working100 atoms of Neon contains 90.92 atoms of 20

10Ne isotopes100 atoms of Neon contains 0.26 atoms of 21

10Ne isotopes100 atoms of Neon contains 8.82 atoms of 22

10 Ne isotopesTherefore;RAM of Neon = (90.92/100 x20) + (0.26/100 x 21) +(8.82 /100 x 22)

= Note that:Relative atomic mass has no unitsMore atoms of Neon exist as 20

10Ne (90.92%) therefore RAM is nearer to the more abundant 20

10Ne isotope.

d) Calculate the relative atomic mass of Argon given that it exist as;90.92% 20

10Ne , 0.26% 2110Ne , 8.82% 22

10Ne,NB

The relative atomic mass is a measure of the masses of atoms. The higher the relative atomic mass, the heavier the atom.

Electrons are found in energy levels/orbital.An energy level is a fixed region around/surrounding the nucleus of an atom occupied by electrons of the same (potential) energy. By convention energy levels are named 1,2,3… outwards from the region nearest to nucleus.

Each energy level is occupied by a fixed number of electrons:The 1st energy level is occupied by a maximum of two electronsThe 2nd energy level is occupied by a maximum of eight electronsThe 3rd energy level is occupied by a maximum of eight electrons( or eighteen electrons if available) The 4th energy level is occupied by a maximum of eight electrons( or eighteen or thirty two electrons if available)

This arrangement of electrons in an atom is called electron configuration / structure.By convention the electron configuration / structure of an atom of an element can be shown in form of a diagram using either cross(x) or dot(●) to

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Practice examples drawing electronic configurations

a)11H has - in nucleus1proton and 0 neutrons

- 1 electron in the 1st energy levels thus:NucleusEnergy levelsElectrons(represented by cross(x)

Electronic structure of Hydrogen is thus: 1:

b) 42He has - in nucleus 2 proton and 2 neutrons

- 2 electron in the 1st energy levels thus:

NucleusEnergy levelsElectrons (represented by cross(x)

Electronic structure of Helium is thus: 2:

c) 73Li has - in nucleus 3 proton and 4 neutrons

- 2 electron in the 1st energy levels -1 electron in the 2nd energy levels thus


Electronic structure of Lithium is thus: 2:1

d) 94Be has - in nucleus 4 proton and 5 neutrons



Electronic structure of Beryllium is thus: 2:2

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e) 115B has - in nucleus 5 proton and 6 neutrons



Electronic structure of Boron is thus: 2:3

f) 126C has - in nucleus 6 proton and 6 neutrons



Electronic structure of Carbon is thus: 2:4

g) 147N has - in nucleus 7 proton and 7 neutrons



Electronic structure of Nitrogen is thus: 2:5

h) 168O has - in nucleus 8 proton and 8 neutrons



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Electronic structure of Oxygen is thus: 2:6

i) 199F has - in nucleus 9 proton and 10 neutrons



Electronic structure of Fluorine is thus: 2:7i) 20

10Ne has - in nucleus 10 proton and 10 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels thus


Electronic structure of Neon is thus: 2:8

j) 2311Na has - in nucleus 11 proton and 12 neutrons

- 2 electron in the 1st energy levels -8 electron in the 2nd energy levels

-1 electron in the 3rd energy levels thus

NucleusEnergy levelsElectrons (represented by dot(.)

Electronic structure of Sodium is thus: 2:8:1

k) 2412Mg has - in nucleus 12 proton and 12 neutrons

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Electronic structure of Magnesium is thus: 2:8:2l) 27

13Al has - in nucleus 13 proton and 14 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels



Electronic structure of Aluminium is thus: 2:8:3

m) 2814Si has - in nucleus 14 proton and 14 neutrons



NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Silicon is thus: 2:8:4

n) 3115P has - in nucleus 14 proton and 15 neutrons



NucleusEnergy levels

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Electrons (represented by dot(.)Electronic structure of Phosphorus is thus: 2:8:5

o) 3216S has - in nucleus 16 proton and 16 neutrons



NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Sulphur is thus: 2:8:6 p) 35

17Cl has - in nucleus 18 proton and 17 neutrons - 2 electron in the 1st energy levels -8 electron in the 2nd energy levels


NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Chlorine is thus: 2:8:7

p) 4018Ar has - in nucleus 22 proton and 18 neutrons



NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Argon is thus: 2:8:8

q) 3919K has - in nucleus 20 proton and 19 neutrons


-8 electron in the 3rd energy levels -1 electron in the 4th energy levels thus

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NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Potassium is thus: 2:8:8:1

r) 4020Ca has - in nucleus 20 proton and 20 neutrons


-8 electron in the 3rd energy levels -2 electron in the 4th energy levels thus

NucleusEnergy levelsElectrons (represented by dot(.)Electronic structure of Calcium is thus: 2:8:8:2

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B.PERIODIC TABLE

There are over 100 elements so far discovered. Scientists have tried to group them together in a periodic table. A periodic table is a horizontal and vertical arrangement of elements according to their atomic numbers.This table was successfully arranged in 1913 by the British scientist Henry Moseley from the previous work of the Russian Scientist Dmitri Mendeleev.The horizontal arrangement forms period. Atoms in the same period have the same the same number of energy levels in their electronic structure. i.e.The number of energy levels in the electronic configuration of an element determine the period to which the element is in the periodic table.e.g.Which period of the periodic table are the following isotopes/elements/atoms?

a) 126C

Electron structure 2:4 => 2 energy levels used thus Period 2b) 23

11Na

Electron structure 2:8:1 => 3 energy levels used thus Period 3c) 39

19K

Electron structure 2:8:8:1 => 4 energy levels used thus Period 4d) 1

1HElectron structure 1: => 1 energy level used thus Period 1

The vertical arrangement of elements forms a group. Atoms in the same have the same the same group have the same number of outer energy level electrons as per their electronic structure. i.e.The number of electrons in the outer energy level an element determine the group to which the element is ,in the periodic table.

a) 126C

Electron structure 2:4 => 4 electrons in outer energy level thus Group IVb) 23

11C Electron structure 2:8:1 => 1 electron in outer energy level thus Group I

c) 3919K

Electron structure 2:8:8:1=>1 electron in outer energy level thus Group I

d) 11H

Electron structure 1: => 1 electron in outer energy level thus Group I

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By convention; (i)Periods are named using English numerals 1,2,3,4,…

(ii)Groups are named using Roman numerals I,II,III,IV,…

There are eighteen groups in a standard periodic table.There are seven periods in a standard periodic table.

When an atom has maximum number of electrons in its outer energy level, it is said to be stable. When an atom has no maximum number of electrons in its outer energy level, it is said to be unstable. All stable atoms are in group 8/18 of the periodic table. All other elements are unstable.All unstable atoms/isotopes try to be stable through chemical reactions. A chemical reaction involves gaining or losing outer electrons (electron transfer) .When electron transfer take place, an ion is formed.

An ion is formed when an unstable atom gain or donate electrons in its outer energy level inorder to be stable. Whether an atom gain or donate electrons depend on the relative energy required to donate or gain extra electrons i.e.Examples

1. 199 F has electronic structure/configuration 2:7.

It can donate the seven outer electrons to have stable electronic structure/configuration 2:.

THE STANDARD PERIODIC TABLE OF ELEMENTS

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It can gain one extra electron to have stable electronic structure/configuration 2:8. Gaining requires less energy, and thus Fluorine reacts by gaining one extra electrons.

2. 2313 Al has electronic structure/configuration 2:8:3

It can donate the three outer electrons to have stable electronic structure/configuration 2:8.It can gain five extra electrons to have stable electronic structure/configuration 2:8:8. Donating requires less energy, and thus Aluminium reacts by donating its three outer electrons.

Elements with less than four electrons in the outer energy level donates /lose the outer electrons to be stable and form a positively charged ion called cation.A cation therefore has more protons(positive charge) than electrons(negative charge) Generally metals usually form cationElements with more than four electrons in the outer energy level gain /acquire extra electrons in the outer energy level to be stable and form a negatively charged ion called anion. An anion therefore has less protons(positive charge) than electrons(negative charge) Generally non metals usually form anion. Except HydrogenThe charge carried by an ion is equal to the number of electrons gained/acquired or donated/lost.

Examples of ion formation

1.11H

H -> H+ + e (atom) (monovalent cation) (electrons donated/lost)

Electronic configuration 1: (No electrons remains)

2. 2713 Al

Al -> Al3+ + 3e (atom) (trivalent cation) (3 electrons donated/lost)

Electron 2:8:3 2:8structure (unstable) (stable)

3. 2311 Na

Na -> Na+ + e (atom) (cation) ( 1 electrons donated/lost)


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4. 2412Mg

Mg -> Mg2+ + 2e (atom) (cation) ( 2 electrons donated/lost)


5. 168O

O + 2e -> O2- (atom) ( 2 electrons gained/acquired) (anion)

Electron 2:6 2:8structure (unstable) (stable)

6. 147N

N + 3e -> N3- (atom) ( 3 electrons gained/acquired) (anion)


7. 3115P

P + 3e -> P3- (atom) ( 3 electrons gained/acquired) (anion)


8. 199F

F + e -> F- (atom) ( 1 electrons gained/acquired) (anion)


9. 3517Cl

Cl + e -> Cl- (atom) ( 1 electrons gained/acquired) (anion)

Electron 2:8:7 2:8:8structure (unstable) (stable)

3. 3919 K

K -> K+ + e (atom) (cation) ( 1 electrons donated/lost)

Electron 2:8:8:1 2:8:8structure (unstable) (stable)

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When an element donate/loses its outer electrons ,the process is called oxidation. When an element acquires/gains extra electrons in its outer energy level,the process is called reduction.The charge carried by an atom, cation or anion is its oxidation state.

Table showing the oxidation states of some isotopesElement Symbol of element / isotopes Charge of ion Oxidation stateHydrogen 1

1H21H(deuterium)

31H(Tritium)

H+

H+

H+

+1+1+1

Chlorine 3517Cl

3717Cl

Cl-

Cl--1-1

Potassium 3919K

4019K

4119K

K+

K+

K+

+1+1+1

Oxygen 168O

188O

O2-

O2--2-2

Magnesium 2412Mg Mg2+ +2

sodium 2311Na Na+ +1

Copper Cu Cu+

Cu2++1+2

Iron Fe2+

Fe3++2+3

Lead Pb2+

Pb4++2+4

Manganese Mn2+

Mn7++2+7

Chromium Cr3+

Cr6++3+6

Sulphur S4+

S6++4+6

Carbon C2+

C4++2+4

Note :Some elements can exist in more than one oxidation state.They are said to have variable oxidation state.

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Roman capital numeral is used to indicate the oxidation state of an element with a variable oxidation state in a compound.

Examples: (i) Copper (I) means Cu+ as in Copper(I)oxide(ii) Copper (II) means Cu2+ as in Copper(II)oxide(iii) Iron (II) means Fe2+ as in Iron(II)sulphide(iv) Iron (III) means Fe3+ as in Iron(III)chloride(iv) Sulphur(VI)mean S6+ as in Iron(III)sulphate(VI)(v) Sulphur(VI)mean S6+ as in sulphur(VI)oxide(vi) Sulphur(IV)mean S4+ as in sulphur(IV)oxide(vii) Sulphur(IV)mean S4+ as in sodium sulphate(IV)(ix) Carbon(IV)mean C4+ as in carbon(IV)oxide(x) Carbon(IV)mean C4+ as in Lead(II)carbonate(IV)(xi) Carbon(II)mean C2+ as in carbon(II)oxide(xii) Manganese(IV)mean Mn4+ as in Manganese(IV)oxide

A compound is a combination of two or more elements in fixed proportions. The ratio of the atoms making a compound is called the chemical formulae. Elements combine together to form a compound depending on their combining power. The combining power of atoms in an element is called Valency.Valency of an element is equal to the number of:

(i)hydrogen atoms that an atom of element can combine with or displace. (ii)electrons gained /acquired in outer energy level by non metals to be stable/attain duplet/octet.(iii)electrons donated/lost by outer energy level of metals to be stable/attain octet/duplet.(iv)charges carried by ions/cations/ions

Group of atoms that react as a unit during chemical reactions are called radicals.Elements with variable oxidation state also have more than one valency.

Table showing the valency of common radicals.

Radical name Chemical formulae Combining power / ValencyAmmonium NH4

+ 1Hydroxide OH- 1Nitrate(V) NO3

- 1Hydrogen carbonate HCO3

- 1Hydrogen sulphate(VI) HSO4

- 1Hydrogen sulphate(IV) HSO3

- 1Manganate(VII) MnO4

- 1

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Chromate(VI) CrO42- 2

Dichromate(VI) Cr2O72- 2

Sulphate(VI) SO42- 2

Sulphate(IV) SO32- 2

Carbonate(IV) CO32- 2

Phosphate(V) PO42- 3

Table showing the valency of some common metal and non metals

Element/metal Valency Element/non metal Valency

Hydrogen 1 Florine 1Lithium 1 Chlorine 1Beryllium 2 Bromine 1Boron 3 Iodine 1Sodium 1 Carbon 4Magnesium 2 Nitrogen 3Aluminium 3 Oxygen 2Potassium 1 Phosphorus 3Calcium 2Zinc 2Barium 2Mercury 2Iron 2 and 3Copper 1 and 2Manganese 2 and 4Lead 2 and 4

From the valency of elements , the chemical formular of a compound can be derived using the following procedure:

(i)Identify the elements and radicals making the compound (ii)Write the symbol/formular of the elements making the compound starting with the metallic element(iii)Assign the valency of each element /radical as superscript.(iv)Interchange/exchange the valencies of each element as subscript.(v)Divide by the smallest/lowest valency to derive the smallest whole number ratios Ignore a valency of 1.This is the chemical formula.

Practice examplesWrite the chemical formula of

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(a)Aluminium oxide

Elements making compound Aluminium OxygenSymbol of elements/radicals in compound Al OAssign valencies as superscript Al3 O2

Exchange/Interchange the valencies as subscript Al2 O3

Divide by smallest valency to get whole number - -

Chemical formula of Aluminium oxide is thus: Al2 O3

This means:2atoms of Aluminium combine with 3 atoms of Oxygen

(b)Sodium oxide

Elements making compound Sodium OxygenSymbol of elements/radicals in compound Na OAssign valencies as superscript Na1 O2

Exchange/Interchange the valencies as subscript Na2 O1

Divide by smallest valency to get whole number - -

Chemical formula of Sodium oxide is thus: Na2 OThis means:2atoms of Sodium combine with 1 atom of Oxygen

(c)Calcium oxide

Elements making compound Calcium OxygenSymbol of elements/radicals in compound Ca OAssign valencies as superscript Ca2 O2

Exchange/Interchange the valencies as subscript Ca2 O2

Divide by two to get smallest whole number ratio Ca1 O1

Chemical formula of Calcium oxide is thus: CaOThis means:1 atom of calcium combine with 1 atom of Oxygen.

(d)Lead(IV)oxide

Elements making compound Lead OxygenSymbol of elements/radicals in compound Pb OAssign valencies as superscript Pb4 O2

Exchange/Interchange the valencies as subscript Pb2 O4

Divide by two to get smallest whole number ratio Pb1 O2

Chemical formula of Lead(IV) oxide is thus: PbO2

This means:1 atom of lead combine with 2 atoms of Oxygen.

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(e)Lead(II)oxide

Elements making compound Lead OxygenSymbol of elements/radicals in compound Pb OAssign valencies as superscript Pb2 O2

Exchange/Interchange the valencies as subscript Pb2 O2

Divide by two to get smallest whole number ratio Pb1 O1

Chemical formula of Lead(II) oxide is thus: PbOThis means:1 atom of lead combine with 1 atom of Oxygen.

(e)Iron(III)oxide

Elements making compound Iron OxygenSymbol of elements/radicals in compound Fe OAssign valencies as superscript Fe3 O2

Exchange/Interchange the valencies as subscript Fe2 O3

Divide by two to get smallest whole number ratio - -

Chemical formula of Iron(III) oxide is thus: Fe2O3

This means:2 atom of lead combine with 3 atom of Oxygen.

(f)Iron(II)sulphate(VI)

Elements making compound Iron sulphate(VI)Symbol of elements/radicals in compound Fe SO4

Assign valencies as superscript Fe2 SO4 2

Exchange/Interchange the valencies as subscript Fe2 SO4 2

Divide by two to get smallest whole number ratio Fe1 SO4 1

Chemical formula of Iron(II) sulphate(VI) is thus: FeSO4

This means:1 atom of Iron combine with 1 sulphate(VI) radical.

(g)Copper(II)sulphate(VI)

Elements making compound Copper sulphate(VI)Symbol of elements/radicals in compound Cu SO4

Assign valencies as superscript Cu2 SO4 2

Exchange/Interchange the valencies as subscript Cu2 SO4 2

Divide by two to get smallest whole number ratio Cu1 SO4 1

Chemical formula of Cu(II)sulphate(VI) is thus: CuSO4

This means:1 atom of Copper combine with 1 sulphate(VI) radical.

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(h)Aluminium sulphate(VI)

Elements making compound Aluminium sulphate(VI)Symbol of elements/radicals in compound Al SO4

Assign valencies as superscript Al3 SO4 2

Exchange/Interchange the valencies as subscript Al2 SO4 3


Chemical formula of Aluminium sulphate(VI) is thus: Al2(SO4)3

This means:2 atom of Aluminium combine with 3 sulphate(VI) radical.

(i)Aluminium nitrate(V)

Elements making compound Aluminium nitrate(V)Symbol of elements/radicals in compound Al NO3

Assign valencies as superscript Al3 NO3 1

Exchange/Interchange the valencies as subscript Al1 NO3 3


Chemical formula of Aluminium sulphate(VI) is thus: Al (NO3)3

This means:1 atom of Aluminium combine with 3 nitrate(V) radical.

(j)Potassium manganate(VII)

Elements making compound Potassium manganate(VII)Symbol of elements/radicals in compound K MnO4

Assign valencies as superscript K 1 MnO4 1

Exchange/Interchange the valencies as subscript K1 MnO4 1


Chemical formula of Potassium manganate(VII) is thus: KMnO4

This means:1 atom of Potassium combine with 4 manganate(VII) radical.

(k)Sodium dichromate(VI)

Elements making compound Sodium dichromate(VI)Symbol of elements/radicals in compound Na Cr2O7

Assign valencies as superscript Na 1 Cr2O7 2

Exchange/Interchange the valencies as subscript Na2 Cr2O7 1


Chemical formula of Sodium dichromate(VI) is thus: Na2 Cr2O7

This means:2 atom of Sodium combine with 1 dichromate(VI) radical.

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(l)Calcium hydrogen carbonate

Elements making compound Calcium Hydrogen carbonate

Symbol of elements/radicals in compound Ca CO3

Assign valencies as superscript Ca 2 HCO3 1

Exchange/Interchange the valencies as subscript Ca1 HCO3 2


Chemical formula of Calcium hydrogen carbonate is thus: Ca(HCO3)2

This means:1 atom of Calcium combine with 2 hydrogen carbonate radical.

(l)Magnesium hydrogen sulphate(VI)

Elements making compound Magnesium Hydrogen sulphate(VI)

Symbol of elements/radicals in compound Mg HSO4

Assign valencies as superscript Mg 2 HSO4 1

Exchange/Interchange the valencies as subscript Mg1 HSO4 2


Chemical formula of Magnesium hydrogen sulphate(VI) is thus: Mg(HSO4)2

This means:1 atom of Magnesium combine with 2 hydrogen sulphate(VI) radical.

Compounds are formed from chemical reactions. A chemical reaction is formed when atoms of the reactants break free to bond again and form products. A chemical reaction is a statement showing the movement of reactants to form products. The following procedure is used in writing a chemical equations:1. Write the word equation2. Write the correct chemical formula for each of the reactants and products3. Check if the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side.4. Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple if the number of atoms on one side is not equal. This is called balancing. Do not change the chemical formula of the products/reactants.5. Assign in brackets, the physical state/state symbols of the reactants and products after each chemical formula as:

(i) (s) for solids(ii) (l) for liquids(iii) (g) for gas

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(iv) (aq) for aqueous/dissolved in water to make a solution.

Practice examples Write a balanced chemical equation for the following

(a) Hydrogen gas is prepared from reacting Zinc granules with dilute hydrochloric acid.

Procedure

1. Write the word equationZinc + Hydrochloric acid -> Zinc chloride + hydrogen gas

2. Write the correct chemical formula for each of the reactants and products Zn + HCl -> ZnCl2 + H2

3. Check if the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side. Number of atoms of Zn on the reactant side is equal to product side One atom of H in HCl on the reactant side is not equal to two atoms in H2 on product side. One atom of Cl in HCl on the reactant side is not equal to two atoms in ZnCl2 on product side.

4. Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple if the number of atoms on one side is not equal. Multiply HCl by “2” to get “2” Hydrogen and “2” Chlorine on product and reactant side.

Zn + 2 HCl -> ZnCl2 + H2

5. Assign in brackets, the physical state/state symbols . Zn(s) + 2 HCl(aq) -> ZnCl2(aq) + H2(g)

(b)Oxygen gas is prepared from decomposition of Hydrogen peroxide solution to water

Procedure

1. Write the word equationHydrogen peroxide -> Water + oxygen gas

2. Write the correct chemical formula for each of the reactants and products H2O2 -> H2O + O2

3. Check if the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side. Number of atoms of H on the reactant side is equal to product side

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Two atom of O in H2O2 on the reactant side is not equal to three atoms (one in H2O and two in O2) on product side. 4. Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple if the number of atoms on one side is not equal. Multiply H2O2 by “2” to get “4” Hydrogen and “4” Oxygen on reactants Multiply H2O by “2” to get “4” Hydrogen and “2” Oxygen on product side When the “2” Oxygen in O2 and the“2” in H2O are added on product side they are equal to the“4” Oxygen on reactants side.

2H2O2 -> 2H2O + O2

5. Assign in brackets, the physical state/state symbols .2H2O2(aq) -> 2H2O(l) + O2(g)

(c) Chlorine gas is prepared from Potassium manganate(VII) reacting with hydrochloric acid to form potassium chloride solution, manganese(II) chloride solution,water and chlorine gas.

Procedure1. Write the word equation

Potassium manganate(VII) + Hydrochloric acid -> potassium chloride + manganese(II) chloride + chlorine +water

2. Write the correct chemical formula for each of the reactants and products KMnO4 + HCl -> KCl + MnCl2 +H2O + Cl2

3. Check if the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side. Number of atoms of K and Mn on the reactant side is equal to product side Two atom of H in H2O on the product side is not equal to one atom on reactant side.Four atom of O in KMnO4 is not equal to one in H2OOne atom of Cl in HCl on reactant side is not equal to three (one in H2O and two in Cl2) 4. Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple if the number of atoms on one side is not equal. Multiply HCl by “16” to get “16” Hydrogen and “16” Chlorine on reactants Multiply KMnO4 by “2” to get “2” Potassium and “2” manganese, “2 x4 =8” Oxygen on reactant side.

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Balance the product side to get:

2 KMnO4 +16 HCl -> 2 KCl + 2 MnCl2 +8 H2O + 5 Cl2

5. Assign in brackets, the physical state/state symbols .2KMnO4(s) +16 HCl(aq)-> 2 KCl (aq) + 2MnCl2(aq)+8 H2O(l)+5 Cl2(g)

(d)Carbon(IV)oxide gas is prepared from Calcium carbonate reacting with hydrochloric acid to form calcium chloride solution, water and carbon(IV)oxide gas.

Procedure1. Write the word equation

Calcium carbonate + Hydrochloric acid -> calcium chloride solution+ water +carbon(IV)oxide

2. Write the correct chemical formula for each of the reactants and products CaCO3 + HCl -> CaCl2 +H2O + CO2

3. Check if the number of atoms of each element on the reactant side is equal to the number of atoms of each element on the product side. 4. Multiply the chemical formula containing the unbalanced atoms with the lowest common multiple if the number of atoms on one side is not equal. 5. Assign in brackets, the physical state/state symbols . CaCO3(s) + 2 HCl(aq) -> CaCl2(aq) + H2O(l) + CO2(g)

(d)Sodium hydroxide solution neutralizes hydrochloric acid to form salt and water.

NaOH(aq) + HCl(aq) -> NaCl (aq) + H2O(l)

(e)Sodium reacts with water to form sodium hydroxide and hydrogen gas.2Na(s) + 2H2O(l) -> 2NaOH(aq) + H2(g)

(f)Calcium reacts withwater to form calcium hydroxide and hydrogen gasCa(s) + 2H2O(l) -> Ca(OH)2(aq) + H2(g)

(g)Copper(II)Oxide solid reacts with dilute hydrochloric acid to form copper(II)chloride and water.

CuO(s) + 2HCl(aq) -> CuCl2(aq) + H2O(l)

(h)Hydrogen sulphide reacts with Oxygen to form sulphur(IV)Oxide and water.

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2H2S(g) + 3O2(g) -> 2SO2(g) + 2H2O(l)

(i)Magnesium reacts with steam to form Magnesium Oxide and Hydrogen gas.

Mg(s) + 2H2O(g) -> MgO(s) + H2(g)

(j)Ethane(C2H6) gas burns in air to form Carbon(IV)Oxide and water.2C2H6(g) + 7O2(g) -> 4CO2(g) + 6H2O(l)

(k)Ethene(C2H4) gas burns in air to form Carbon(IV)Oxide and water.C2H4(g) + 3O2(g) -> 2CO2(g) + 2H2O(l)

(l)Ethyne(C2H2) gas burns in air to form Carbon(IV)Oxide and water.2C2H2(g) + 5O2(g) -> 4CO2(g) + 2H2O(l)

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TOPICAL QUESTIONS ON THE TOPIC BASED ON PAST KCSE PAPERS 1. Complete the table below. (1 ½ mks)

Isotope Number ofProtons Neutrons Electons

59 Co27

2. The electron arrangement of ions X3 + and Y-2 are 2:8 and 2:8:8 respectively.a) Write the electron arrangement of elements “X” and “Y” (2mks)b) Write the formula of the compound that would be formed between X and Y.

(1mk)3. With reference to its atomic number of one explain why hydrogen can be placed in

either group I or VII on the periodic table. (2mks)4. An element Y has the electronic configuration of 2:8:5

a) Which period of the periodic table does the element belong. (1mk)b) Write the formula of the most stable anion formed when element Y ionizes.

(1mk)c) Explain the difference between the atomic radius of element Y and ionic

radius. (1mk)5. 34

An ion of phosphorous can be presented as P -3

15Draw a diagram to show the distribution of the electrons and the composition in the nucleus of the ion of phosphorous. (2mks)

6. The grid below shows part of the periodic table. The letters do not represent the actual symbols of the element.

GH I

Fa) Select

i) Element which has the largest atomic radius (1mk)ii) Most reactive non- metal

b) Show on the grid the position of element “J” which forms J-2 ions with electronic configuration 2:8:8:8 (1mk)

7. Study the information in the table below and answer questions that follows;Ions Electron arrangement Ionic radiusNa+ 2,8 0.95K2+ 2,8,8 0.133Mg2+ 2,8 0.065

Explain why the ionic radius ofa) K+ is greater than that of Na+ (1mk)b) Mg2+ is smaller than that of Na+ (2mks)

29

8. An atom of hydrogen can form two ions. Write down two equations to show how the neutral atom of each case show the sign of the energy change involved. (2mks)

9. Brass is an alloy of zinc and copper. Give one used brass (1mk)10. Use the information in the table below to answer questions that follows. That

follows. The letters do not represent the actual symbols of the elements. Elements B C D E FAtomic numbers 18 5 3 5 20Mass Numbers 40 10 7 11 40

a) Which two letters represent the same element? Give a reason (2mks)b) Give the number of neutrons in an atom of element D (1mk)

11. The table below gives some information about elements I, II, III and IV which are in the same group of the periodic table.Use the information to answer the questions that follows.

Element First ionization energy K 5 mol -1 Atomic radius (nm)I 520 0.15II 500 0.19III 420 0.23IV 400 0.25

State and explain the relationship between the variation in the first ionization energies and the atomic radii. (3mks)

12. The table below shows the relative atomic masses and the percentage abundance of the isotopes L1, L2 of element L

Relative atomic masses % abundanceL1 62.93 69.09L2 64.93 30.91

Calculate the relative atomic mass of element L. (3mks)13. Explain why there is general increase in the first ionization energies of the elements in

period 3 of the periodic table from left to right. (2mks)14. The table below shows the number of valance electrons of the elements P, Q and R.

Element P Q R

Number of valence electrons 3 5 2

a) Explain why P and R would not be expected to form a compound. (1mk)b) Write an equation to show the effect of heat on the carbonate of R (1mk)c) Write the formula for the most stable ion or Q. (1mk)

15. a) What are isotopes? (1mk)18

b) Determine the number of neutrons in O 8 (1mk)

30

16. The grid below is part of the periodic table. Use it to answer the questions that follow. (The letters are not the actual symbols of the elements)

R SN Q T UP

a) Indicate on the grid the position of an element represented by letter V whose atomic number is 14. (1mk)

b) Select a letter which represents a monoatomic gas. (1mk)c) Write an equation for the reaction between Q and T. (1mk)

17. The table below gives elements represented by letters T, U, V, w, x, Y their atomic numbers.

Elements T U V W X YAtomic numbers 12 13 14 15 16 17Electronic arrangement

Use the information in the table to answer the questions belowa) Complete the above table giving the electron arrangement of each of the

element (2mks)b) In which period of the periodic table do these elements belong? Give a reason.

(2mks)c) How does the atomic radius of V compare with that of X. Explain? (2mks)d) Give the formula of the compound that could be termed between “U” and “W”

(1mk)e) What type of bonding will be present in a compound formed between T and

Y? Explain (2mks)f) Arrange the species T2+ T+ and T in increasing order of sizeg) Which are the ions X+2

and X-2 is most suitable? Explain (2mks)h) Give the fomula of

i) An acidic oxide formed when one of the elements in the table is heated in air (1mk)

ii) A basic oxide formed when one of the elements in the table is heated in the air. (1mk)

18. Study the table below and answer the questions that follows:-Elements Atomic numbers Relative atomic mass Melting point 0CAluminium 13 27.0 1020Calcium 20 40.0 850Carbon - 12.0 3730Hydrogen - 1.0 -249Magnesium 12 24.3 650Neon 10 - -249Phosphorus 15 31.0 442 white

590 redSodium - 23 97.8

a) Complete the table by filling in the missing atomic numbers and atomic masses (2mks)

b) Write the electron arrangement for the following ions

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i) Ca2+ (1mk)ii) P-3 (1mk)

c) What is the melting point of hydrogen in degrees Kelvin (1mk)d) Which of the two allotropes of phosphorous has a higher density? Explain

(2mks)e) The mass numbers of the three isotopes of magnesium are 24, 25 and 26.

What is the mass number of the most abundant isotope of Magnesium? Explain (2mks)

f) Give the formula to the compound formed between aluminium and carbon.(1mk)

19 The grid given below represents part of the periodic table. Study it answer the questions that follows. The letters do not represent the actual symbols of the elements.

C BF D E

i) What name is given to the group of elements to which “C” and “F” belong? (1mk)

ii) Which letter represents the element that is least reactive? Explain. (2mks)iii) What type of bond is formed when B and E reacts? Explain. (2mks)iv) On the grid indicate with a tick the position of an element G which is in the

third period of the periodic table and terms G-3 ion. (1mk)20. Study the information in the table below and answer the questions that follow. The

letters do not represent the actual symbols of the elementsElements Electronic configuration Ionization energy kj mol -1

P 2,1 519C 2,8,1 494R 2,8,8,1 418

i) What is the general name given to the group which elements P, C and R belongs? (1mk)

ii) What is meant by ionization energy (2mks)iii) Explain why element p has the highest ionization energy. (2mks)iv) a) When a piece of element “C” is placed on water. It melts and

hissing sound is produced as it moves on the surface of the water. Explain these observations (2mks)

b) Distinguish between a strong and a weak base. Give an example of each. (2mks)

c) Neutralization is one of the methods of preparing salt i) What is meant by neutralization (1mk)ii) Describe how you would prepare crystals of sodium nitrate

starting with 200 cm3 of 2m sodium hydroxide. (3mks)iii) Write an equation for the reaction that takes place when a solid

sample of sodium nitrate is heated. (1mk)21. a) The chart below is an outline of part of the periodic table

32

i) With the help of vertical and horizontal lines, indicate the direction of increasing metallic nature of elements. (2mks)

ii) Which type of elements are represented in the shaded area? (1mk)b) i) Element “A” is in the same group of the periodic table as chlorine.

Write the formula of the compound formed when “A” react with potassium metal (1mk)

ii) What type of bonding exists in the compound formed in b (i) above? Give a reason for your answer (3mks)

c) Starting with aqueous magnesium sulphate, describe how you would obtain a sample of magnesium oxide. (3mks)

d) Write two ionic equations to show that aluminium hydroxide is amphoteric 22. Brine usually contain calcium and magnesium salts. Explain how sodium carbonate

is used to purify brine. (2mks)23. The table below gives information about elements A1, A2, A3 and A4

Element Atomic number Atomic radius (nm) Ionic radius (nm)A1

A2

A3

A4

351317

0.1340.0900.1430.099

0.0740.120.0500.181

i) In which period of the periodic table is element A2

Give reason. (2mks)ii) Explain why the atomic radius of:

I. A1 is greater than that of A2 (2mks)II. A4 is smaller than its ionic radius. (2mks)

iii) Select the element which is in the same group as A3 (1mk)iv) Using dots (.) and crosses (x) to represent outermost electrons, draw a diagram

to show the bonding in the compound formed when A1 reacts with A4

24. Using the table below explain the followingIons Na+ Mg2+ Al3+ K+

Ionic radius 0.086 0.073 0.064 0.097a) Ionic radius of Na+ is less than that of K+. Explain (1mk)b) Sodium, magnesium and aluminium belong to the same period in the periodic

table. Explain the trend in their ironic radii. (3mks)25. Study the information in the table below and Answer questions that follows.

W X Y ZGlows red hot when heated.Does not react with

Forms a ball on the surface of water and react.

Burns with dazzling fame and does not react with cold water.

Burns with a red flame and produce hydrogen with cold water.

33

water but turns red brown on surface when left outside over night.

Produce a hissing sound.Burning in air with a yellow orange flame.

a) Identify the above metals (1 ½mks)b) Arrange the metals according to their reactivity starting with the most reactive.

26. Element Z in the second period of the periodic table forms Z 3+ ions using (x) to represent electrons; draw a complete structure of an isotope of “Z” having mass number 8. (3mks)The table below gives information on the some elements. The letters are not actual symbols of the elements. Study it and it to answer the questions that follow.

Elements Ionization energy (k j) Atomic radius (NM) Ionic radius (NM)L 410 0.154 0.091G 380 0.192 0.097Q 490 0.108 0.086

a) Select the most reactive element and give reasons for your answer. (2mks)b) Do this element represent metallic or nonmetallic group. Explain. (2mks)

27. The table below shows part of periodic table for some elements represented by Q, R, T, V, W, X, Y and Z. The letters do not represent the actual symbols of the elements. Study it and answer the questions that follows.

T1 T1 2Q3 4 5 W6 7 8 V9 10R11 12 13 14 15 16 X17 Y18

19 20a) i) Explain why element T has been placed in two positions in the

periodic table. (1mk)ii) What is the name of the chemical family to which q and R belong?iii) Elements Y is generally unreactive. Explain (1mk)

b) i) Explain the difference in atomic radius of atoms of elements X and Y. (1mk)

ii) V is more reactive than W Explain (1mk)c) i) Draw cross (x) and dots (.) diagram to show bonding between

“W” and “T” to form compound WT4 (2mks)ii) Explain why WT4 have low melting point and does not dissolve in

water (2mks)d) Element X consist of two isotopes whose mass numbers are 35 and 37 exist in

the ratio of 3:1 respectively.i) Draw the atomic structure of the isotope whose mass number is 35 and

atomic structure of the isotope whose mass number is 35 and atomic number 17. (2mks)

ii) Determine the relative atomic mass of element X (2mks)28. a) What is an isotope?

b) Determine the relative atomic mass of argon whose isotope mixture is36. Ar (0.34%) 38Ar (0.06%) 40 Ar (99.6%)18 18 18

29. An element “z” has a mass number of 33 and has 18 neutrons

Iron and Sulphur mixture Gas P

Heat

Compound T

HCL

Gas U + Fecl2HCL

34

a) What is the atomic number of element Z? (1mk)b) Write an equation to show how atom of “z” forms an ion. (1mk)

30. Study the flow chart below and answer the questions that follows-:

a) Namei) Gas P (1mk)ii) Compound T (1mk)iii) Gas U (1mk)

b) Give the chemical test that you would use to identify i) Gas P (1mk)ii) Gas U (1mk)

31. Element E has atomic numbers 15a) Write the electronic arrangement for an atom of “E” (1mk)b) Explain why “E” forms a chloride which is a liquid of low boiling point.

(2mks)32. An element “H” consist of isotopes of mass “10” and “11” with a percentage

composition of 18.7% and 81.3% respectively. Determine the RAM of H. (2mks)

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ANSWERS1. Proton = 27

Neutrons =32Electrons = 27

2. a) X= 2:8::3Y= 2:8:6

b) X2Y3

3. Hydrogen can gain one electron when combined with electronegative element to form H. Hence behave like group seven elements can also lose one electron to form H+ i.e, behave like group one element.

4. a) Period 3b) Y-3

c) The ionic radius of Y is greater than its atomic radius Y reacts by gaining three electrons. The electrons added increases the repulsion / screening effect between the adjacent energy levels.

5.

6. a) i) F, (ii) ib) J is in-group VI, period 3

7. a) K+ has many electrons thus many energy levels. Na+ has few number of electrons and thus few energy levels.

b) Mg2+ contain large number of protons compared to Na+ i.e the effective nuclear charge of Mg+2 ions is high, thus results into strong force of attraction between the nucleus and the electrons in their energy levels. Hence they are pulled close to the nucleus.

8. H(g) + e H(g) ∆H -veH e + H+ ∆H = +ve

9. -Coinage, ornaments, soldering-Making, plumbing joints/musical instruments casing for bullets and bombs.

10. a) C and E contain equal numbers of protons/ atomic numbers.b) (I) Neutrons in b = 4

(II) First ionization energy decreases with increase in atomic radius. When atomic radius increases the outermost electrons get further from the nucleus, less energy is thus required to remove it.

11 RAM = (62.93 x 69.09) + (64.93x 30.91) = 63.54100

12. Across the period there is a gradual increase in number of proteins in the nucleus. This increases the force as attraction between the nucleus and the electrons.

13. a) They are both metals and need to lose electrons to be stable

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b) RCO3 (s) RO (s) + CO2 (g)

c) Q -3

14. Atoms of the same element s with the same atomic numbers but different mass numbers.

15. a)

R SN Q V T UP

b) Uc) Q(s) + T2(g) QT2(s) Or Mg(s) + Cl2(g) MgCl2(s)

16. a) T 2:8:2U 2:8:3V 2:8:4W 2:8:5X 2:8:6Y 2:8:7

b) Perion 3, they all contain three energy levels,c) X has a small atomic radius compared to V. X has more protons so

nuclear charge is higher hence attract outmost electrons more strongly.d) U We) Ionic bond/ electrovalent bond “T” will react with “Y” by donating its outer

electrons to the atoms of “Y”f) T2+, T+2, T

(G) X -2 because it has a stable electronic arrangement of 2:8:8 X +2 has unsuitable electronic arrangement o (2:8:4)

h) i) Acidic oxide VO2, W2O 3 XO ii) Basic Oxide TO

17. a) C =6H=1Na=11Ne= 20

b) Ca2+ 2:8:8P-3 2:8:8

c) -259 + 273 = 14kd) Red phosphorous because it has a higher melting point.e) The one atomic number 24, because it is closer to the relative atomic mass

(24.3), that means that it contribute to RAM more than the other two.f) Al4C3

18. (i) Alkaline earth metals.(ii) A: It has a stable electronic arrangement (duplet)(iii) Covalent bond. This because electrons are shared between B and E.

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(iv) G belong to group V, period 319. a) i) Alkaline metals

ii) Energy required to remove an electron from an atomiii) “P” has the smallest ionic radius therefore, the outermost electrons are

most strongly attracted to the nucleus, hence more energy is required to remove this electron.

iv) Melts because the reaction is exothermic. Hissing sound because of the production of hydrogen gas. Float because it is less dense that water. Moves about due to propelling effect of escaping hydrogen.

b) A strong base ionizes completely in water producing more OH- ions e.g KOH and NaOH. A weak base ionizes slightly producing few OH ions e.g NH4 OH, Ca (OH)2 and Mg (OH)2

c) i) Reaction between H+ ions from the acid and OH ions from bases to form 1 mole of water.H+

(aq) + OH (aq) H2O(l)

ii) Add 200cm3 of nitric acid to 200cm3 of 2m sodium hydroxide. Heat the mixture so as to make it saturated /concentrated. Allow the mixture to cool for crystals to appear. Filter/decant to obtain the crystals to appear. Filter /decant to obtain the crystals.

iii) NaNo3(s) NaNO2(aq) + O2(g)

20. a) i)

ii) Non metalsb) i) KA// KBr//KI any one

ii) Ionic/ electrovalent: “K” loss of electron to form K+ ions. “A” gains electrons to form A ions. Two ions combine to give KA.

c) Add strong alkaline solution KOH //NaOH to Magnesium Sulphate solution to precipitate Mg (OH)2.(s). Filter the filtrate to remove water. The residue is magnesium Hydroxide. Heat the hydroxide to remove water.Or Add soluble carbonate or hydrogen carbonate to the mixture. Magnesium carbonate will be formed. Heat the carbonate to get magnesium oxide.

d) Al (OH)3(aq) + 3H+(aq) Al3+

(aq) + 3H2O(i)

Al (OH)3 (s) + OH-

(aq) Al(OH) -4(aq)

21. Add aqueous sodium carbonate to precipitate calcium carbonate and magnesium carbonate and then filter to obtain pure brine.

22. a) Na+ ions contain few electrons compared to K+ which has large number of electrons. Na+ has few energy levels.

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b) The ionic radius decreases from Na+ Alst . This is because there is gradual

increase in numbers of protons in the nucleus. The added proton increases the attraction force between the nucleus and electrons.

23. a) W =FeX =NaY =MgZ =Ca

b) X, Z, Y, W24.

25. a) “G” it requires less ionization energy to pull out first electrons.b) Metallic group: atomic radius is large that the ionic radius.

26. a) i) “T” gain either react by gaining or loosing electrons depending on the electro negativity of the element it is reacted with.

ii) Alkali metalsiii) “Y” is unreactive because it has stable electron arrangement i.e

octet structure.b) i) “Y” has a small atomic radius compared to X. Y has many number

of protons in its nucleus hence attract electrons very strongly towards the nucleus.

ii) “V” has a small atomic radius compare to “W”. It can pull electrons to be gained very strongly i.e it has more electronegative. W can only react by sharing electrons.

c) i)

ii) WT4 is non polar molecule hence cannot dissolve in wate. It exist in form of simple molecular structure hence melting point is low.

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d) i)

ii) (35x3) + (37x1) = 35.54

27. a) Isotopes refer to atoms of the same element with the same atomic numbers but different mass numbers.(36 x0.34) + (38x0.06) + (40x 99.6) = 39.88

10028. a) 33-18=15

b) Z(g) + 3e Z-3(g)

29. a) i) Hydrogen has (H2)ii) Iron (II) Sulphide (Fes)iii) Hydrogen Sulphate (H2S)

b) i) Burns with a pop sound ii) Darken the paper which is soaked in lead acetate: (forms black

precipitate with lead (Pb2+) salts).30. a) E= 2,8,5

b) The chloride of E is in form of a simple molecular structure. The force holding the molecules together is weak van der waals forces.

31. (10x18.7)+ (11 x 81.3) = 10.81100

Atomic structure and periodic table · Web viewWrite the word equation Potassium m anganate(VII) +...

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