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PERIODIC TABLE OF ELEMENTS
B. GROUP 18 ELEMENTS
1. The elements in Group 18 are
Helium 2Neon 2.8
Argon 2.8.8 Krypton 2.8.18.8
Xenon 2.8.18.18.8
Radon 2.8.18.32.18.8
2. They are also known as noble gases, which are chemicallyunreactive. Noble gases are monoatomic.
3. Helium has two valence electrons. This is called dupletelectron arrangement.
4. Other noble gases have eight valence electrons. This is calledoctetelectron arrangement.
5. Duplet and octet electron arrangements are very stablebecause the outermost occupied shells are full.
6. All nobles gases are inertwhich means chemically unreactive.
BECAUSE THE OUTERMOST OCCUPIEDSHELLS ARE FULL
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Why noble gases exist as monoatomic
gases and are chemically unreactive?
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Argon To fill light bulbs, it can last longer
To provide inert atmosphere for welding at high
temperature.
Krypton Used in lasers to repair the retina of the eye.
To fill photographic flash lamps.
Radon
Used in treatment of cancer.
Xenon
Used in bubble chambers in atomic energy reactors.
Hw: QR B pg. 65 no. 1,2
PERIODIC TABLE OF ELEMENTS
C. GROUP 1 ELEMENTS
7. The elements in Group 1 are
Lithium 2.1Sodium 2.8.1Potassium 2.8.8.1
Rubidium 2.8.18.8.1Caesium 2.8.18.18.8.1Francium 2.8.18.32.18.8.1
8. They are also known as alkali metals which react with water toform alkaline solutions.
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9. All Group 1 elements have one valence electron in theiroutermost occupied shells.
Physical Properties of Group 1 Elements1. Group 1 elements are soft metals with lowdensities and
lowmelting points as compared to other metals such as ironand copper.
2. They have silvery and shiny surfaces.
3. They are goodconductor of heat and electricity.
Table 1: Physical Properties of Group 1 Elements
6. From Table 1, when going down the group, atomic size anddensity increase.
7. When going down the group, melting points and boiling points
decrease
Chemical Properties of Group 1 Elements
Elements/symbol
Electronarrangement
Atomicradius(nm)
Meltingpoints(C)
Boilingpoints(C)
Density(g cm-3)
Lithium, Li 2.1 0.15 180 1336 0.57
Sodium, Na 2.8.1 0.19 98 883 0.97
Potassium, K 2.8.8.1 0.23 64 756 0.86
Rubidium, Rb 2.8.18.8.1 0.25 39 701 1.53
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Lithium, sodium and potassium have similar chemicalpropertiesbut differ in reactivity.
Let us carry out this Experiment!Practical Book Experiment 4.1, page 35Activity 4.3, page 38
1. Alkali metals react vigorously with water to produce alkalinemetal hydroxide solutions and hydrogen gas.
Chemical equation;
2Li + 2H2O 2LiOH + H2Lithium Water Lithium Hydrogen
hydroxide gas
2Na + 2H2O 2NaOH + H2
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Sodium Water Sodium Hydrogenhydroxide gas
2K + 2H2O 2KOH + H2
Potassium Water Potassium Hydrogenhydroxide gas
2. Alkali metals react rapidly with oxygen gas, to produce whitesolid metal oxides.
Chemical equations;
4Li + O2 2Li2OLithium Oxygen Lithium
gas oxide
4Na + O2 2Na2OSodium Oxygen Sodium
gas oxide
4K + O2 2K2OPotassium Oxygen Potassium
gas oxide
3. Alkali metals burn in chlorine gas to form white solid metalchlorides.
Chemical reaction;
2Li + Cl2 2LiClLithium Chlorine Lithium
gas chloride
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2Na + Cl2 2NaClSodium Chlorine Sodium
gas chloride
2K + Cl2 2KClPotassium Chlorine Lithium
gas chloride
4. Alkali metals burn in bromine gas to form metal bromides.
For example,
2Li + Br2 2LiBrLithium Bromine Lithium
gas bromide
2Na + Br2 2NaBrSodium Bromine Sodium
gas bromide
2K + Br2 2LiBrPotassium Bromine Potassium
gas bromide
5. Therefore, alkali metals have similar chemical properties.
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Whyalkali metals have similarchemical properties?
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Alkali metals have one valence electron in their outermostoccupied shells.
Each of them reacts by donating one electron from its
outermost occupied shell to form an ion with a charge of+1,thus achieving the stable electron arrangement of the atom ofnoble gas.
Li Li+ + 1e-
2.1 2
Na Na+ + 1e-2.8.1 2.8
K K+ + 1e-
2.8.8.1 2.8.8
6. The reactivity of Group 1 elements increases down the group.
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WhyThe reactivity of Group 1elements increases down the group?
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Going down Group 1, the atomic size (atomic radius)increases.
The single valence electron in the outermost occupied shell
becomes furtheraway from the nucleus
Hence, the attraction between the nucleus and the valenceelectron becomes weaker
Therefore, it is easier for the atom to donate the single valenceelectron to achieve the stable electron arrangement.
Safety precautions in handling Group 1 elementsAlkali metals are very reactive. Safety precautions must be taken whenhandling alkali metals.
The elements must be stored in paraffin oil in bottles Do not hold alkali metals with your bare hands Use forceps to handle them Wear safety goggles
Wear safety gloves Use a small piece of alkali metal when conducting experiments
Hw: QR C pg. 69 no. 1,2,3
PERIODIC TABLE OF ELEMENTS
D. GROUP 17 ELEMENTS
1. The group 17 elements are:
Flourine 2.7
Chlorine 2.8.7
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Bromine 2.8.18.7
Iodine 2.8.18.18.7
Astatine 2.8.18.32.18.7
2. Group 17 elements are known as halogens
3. Halogens exist as diatomic molecules.
4. Halogens have seven valence electrons.
Physical Properties of Group 17 Elements
1. All Group 17 elements are non-metals.
Element SymbolProton
Number
Physicalstate atroom
temperature
ColourMeltingpoint
Boilingpoint
Flourine F 9 Gas Pale yellow
Increase IncreaseChlorine Cl 17 Gas
Greenish-yellow
Bromine Br 35 LiquidReddish-
brown
Iodine I 53 SolidPurplish-
black
2. Halogen have low melting and boiling points becausetheir molecules are attracted to each other by weakforces. Less energy is needed to overcome the forces .
3. When going down the group, the melting and boilingpoints increases. This is because the molecular sizeincreases.
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Diagram:
Chemical Properties of Group 17 Elements
1. Group 17 elements react with water, metal and alkali.
a) Halogen react with waterto form 2 acids
In general:
X2 + H2O HX + HOX ; X is halogen
HX and HOX solutions are acidic. HOX solution exhibits bleaching
properties.
Example:
Cl2 + H2O HCl + HOCl
Chlorine Water Hydrochloric Hypochlorus
Cl2
Cl2
Cl2
Cl2
van derWaalsforces
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What is physicalstate of astatine?
Practical book Carry out anexperiment 4.2 page 39
HW: Draw diagram and answerthe question
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acid acid
Br2 + H2O HBr + HOBr
Bromine Water Hydrobromic Hypobromus
acid acid
I2 + H2O HI + HOI
Iodine Water Hydrobromic Hypoiodus
acid acid
b) Halogens in gaseous state react with hot iron
To form a brown solid , iron(III) halides.
In general:
2Fe + 3X2 2FeX3 ; X is halogen
Example :
2Fe + 3Br2 2FeBr3Iron Bromine Iron(III) bromide
2Fe + 3Cl2 2FeCl3Iron Chlorine Iron(III) chloride
2Fe + 3I2 2FeI3
Iron Iodine Iron(III) iodide
c) Halogens react with sodium hydroxide solution , NaOH.
To form sodium halide, sodium halate and water
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The halogens are decolourised during these reaction.
In general:
X2 + NaOH NaX + NaOX + H2O
[X is halogen]
Example:
Chemical Properties of Group 17 Elements
Fluorine is the mostelectronegative element
Elelctronegativity of an element refers to the measurement of the
strength of an atom in its molecule to attract electrons towards itsnucleus.
WHY they have similar chemical properties???
Halogens have 7 valence electrons.
When halogens take part in chemical reactions, their atomalways gain one electron to achieve a stable octet electronarrangement.
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2 NaOH + I2 NaI + NaOI + H2O
Chlorine, Bromine and Iodine have similar
chemical properties but differ in reactivity.
The Reactivity of Halogens decrease down the group.
Do You Know WHY???
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The explanation
a) The atomic size increases down the group.
b) The distance of the outermost shell becomesfurther from the nucleus.
c) The force of attraction of the nucleus on the electronsof the outermost shell decrease.
d) The tendency of an atom to receive one electron toachieve an octet electron arrangement decrease
Safety Precautions in handling Group 17 elements
1. The vapour of Flourine, Chlorine and Bromine arepoisonous.
2. The following precaution should be taken when handlinghalogen:
a) Halogen gas and liquid should be handled inside afume chamber
b) Wear safety goggles when handling halogen fumes.
c) Wear safety gloves when handling halogen materials.
Do It Yourself
Element X Y Z
Proton number 9 17 35
1. Elements X, Y and Z are same group in the periodictable.
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a. What is the valence electron of the elements X,Y andZ?
seven(7)
b. Which group in the periodic table can you find theelements X,Y and Z?
group 17
c. Element Y can react with water. What are the
properties of the solution produced?
Acidic and bleaching properties
d. Write an equation for the reaction between element Zand hot iron.
2Fe + 3Z2 2FeZ3
3. List all halogen elements from the top to the bottom ofgroup 17.
Flourine, Chlorine, Bromine, Iodine and Astatine
4. Which are the most reactive and least reactivehalogen?
Most reactive: Flourine least reactive : Astatine
4. Write the chemical equations for the following reaction:a) Chlorine with water
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Cl2 + H2O HCl + HOCl
b) bromine with iron
2 Fe + 3Br2 2FeBr3
c) iodine with sodium hydroxide
2 NaOH + I2 NaI + NaOI + H2O
5. Explain the changes to the reactivity of halogens when
going down group 17.
The atomic size of halogen increases down the group.
The distance of the outermost shell becomes furtherfrom the nucleus.
Therefore, the force of attraction of the nucleus on the
electrons of the outermost shelldecrease.
The tendency of an atom to receive one electron toachieve an octet electron arrangement decrease. Thiscauses the reactivity to decrease down the group.
PERIODIC TABLE OF ELEMENTS
E. Elements in a PERIOD 3
Elements in period 3
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Na Mg Al Si P S Cl Ar
2.8.1 2.8.2 2.8.3 2.8.4 2.8.5 2.8.6 2.8.7 2.8.8
Physical properties
symbol Na Mg Al Si P S Cl Ar
Proton number 11 12 13 14 15 16 17 18
Atomic radius (pm) 186 160 143 118 110 104 100 94
electronegativity 0.9 1.2 1.5 1.8 2.1 2.5 3.0 -
Melting point (oC) 98 650 660 1411 44 115 -101 -189
Boiling point (oC) 892 1105 2517 3231 280 444 -34 -186
Metal properties- element in period 3 can be classified into three type
metal : Na, Mg, Al
semi-metal : Sinon-metal : P, S, Cl, Ar
- the metal oxides are usually basic
- non-metallic oxides are acidic oxide
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The oxide of the elements changes from basic to amphoteric and
then acidic across the eriod.
SO2 (p) + H2O (ce) H2SO3 (ak)
Na2O (p) + H2O (ce) 2NaOH (ak)
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- Aluminium oxide, Al2O3 is an amphoteric
i. Aluminium oxide is a bases/alkaly when reacted with acid.
ii. Aluminium oxide is an acid when react with alkali.
Proton number
Size of atom
why?- All the element in period 3 have three filled electron shell butthe proton is increasing by one unit across the period
- As a result, the increase of proton number is increasing theelectrostatic force between the nucleus and the valenceelectron
- The valence electron are pulled closer to the nucleus,causing the atomic radius to decrease
Electronegativity
why?
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Amphoteric oxides is oxide that had acidic and basic properties
Al2O3 (p) + 6HCl (ak) 2AlCl (ak) + 3H2O (ce)
Al2O3 (p) + 2NaOH (ak) + 3H2O (ce) 2NaAl(OH)4 (ak)
Proton number is increasing at one unit when across the period
The atomic radius is decreasing when across the period
The electronegativity increases across the period
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- Electronegativity is a measurement of the tendency of anelement to attract the electrons
- The force of attraction of the nucleus is increase whenacross the period because the size of atomic radius is
decreasing and the proton number is increasing.
Uses of semi-metals- Silicon is a semi-metal, known as metalloid.- Silicon is use in microelectronic industry like transistor,diode
and another electronic component.- Silicon can be built onto a crystal of silicon to make a
microchip.
PERIODIC TABLE OF ELEMENTS
E. Transitions Elements
Transitions elements are elements from group 3 to Group 12.
Character:
- solid with shiny surfaces- ductile- malleable- high tensile strength- high melting and boiling points- high densities- good conductors of heat and electricity
(typical character of metals)
How to differentiate transition metal from other metal?
Three special characteristic for transition elements
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1. Transition elements show different oxidation number intheir compounds.
2. Transition elements form coloured ions or compounds.3. Transition elements and their compounds are useful
catalyst.1. Transition elements show different oxidation number in their
compounds.
They exhibit a wide range ofoxidation states or positively chargedforms. The positive oxidation states allow transition elements toform many different ionic and partially ionic compounds.
All the transition elements except scandium and zinc havemore than one oxidation number.
For example iron. Iron have 2 oxidation number as iniron(II), Fe2+ and iron(III), Fe3+
Example:
Compound Formula Oxidation number
Iron(II) sulphate FeSO4 +2Iron(III) chloride FeCl3 +3
Copper(I) oxide Cu2O +1
Copper(II) sulphate CuSO4 +2
Manganese(II) sulphate MnSO4 +2
Manganese(IV) oxide MnO2 +4
2. Transition elements form coloured ions or compounds
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Do you know why the gemstoneshave different colour?
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Gemstones
Transition metals solutions
http://chemistry.about.com
3. Transition elements and their compounds are useful catalyst
Ruby Emerald Sapphire Amethyst
cobalt(II) nitrate(red)
potassium dichromate(orange)
potassium chromate(yellow)
nickel(II) chloride(light blue)
copper(II) sulfate(blue)
potassium permanganate(purple)
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Catalyst: Chemical substance use to speed up the chemicalreactions
A specific catalyst is used for a specific reaction.
Example
Process Catalyst To produce
Haber Process Iron filling, Fe Ammonia
Contact Process Vanadium(v) oxide, V2O5 Sulphuric acid
Ostwald Process Platinum, Pt Nitric acid
Hydrogenation Nikel, Ni Margarine
Transitions elements are widely used in our daily lives.
Chapter 4 : Periodic Table of Elements
Exercise :
1. Below is a list of elements represented by the symbols as shown:
P11 , Q
12
6 , R19
9 , S27
13 , T35
17 , U39
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(a) Pick a pair of elements that belongs to the same Group in the Periodic Table.
Explain your answer.
[2 m
(b) State the
Group in which element Q belongs to.
[
Period in which element Q belongs to.
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[
(c) State elements which are
(i) metals :
(ii) non-metals :
[2
(d) Which element will form amphoteric oxide?
Which element reacts with cold water?
Write a balanced chemical equation for the reaction.
(f) Write the formula of the ion formed by element S.
Explain the meaning of the term electronegativity.
Which of the two elements R and T is more electronegative?
Explain your answer in (g)(ii).
[2
Which of the two elements S and T has smaller atomic size?
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