Inorganic

Physical Organic Analytical Biochemistry

Mass : quantity of matter

Matter

Solid Liquid Gas

MeltingHeat

Solid Liquid

Cool Solidification

EvaporationHeat

Liquid Vapor

Cool Condensation

Physical state and Changes in Matter

Heat Solid Vapor

Cooling Sublimation

Physical state and Changes in Matter

Heat Ice Water

Cool

HOMOGENEOUS

SUBSTANCES

HETEROGENEOUS

MIXTURE

SOLUTIONSHomogeneous

mixture of variable composition.

Can be separated into

PURESUBSTANCES

Homogeneous matter of fixed composition

COMPOUNDSComposed of 2 or more elements.

Can be separated into

ELEMENTS

Heterogeneous and Homogeneous

Solutions, Pure Substanceand Compounds

MassA mass of an object pertains to the quantity of the matter that object contains.

A physical property that every Manager possesses is a mass.

The amount of mass in a pizza will never change when the object is moved from place to place.

A physical property that is related to mass is weight The weight of a chef may change if it is moved to Uranus because weight is determined by gravity.

Atoms are the basic building blocks of all the chalk around you. It is the smallest particle of matter that can enter into chemical combinations with other particles.

A smallest particle of an element or compound that can have a stable independent existence.Atoms make up molecules. Molecules make up a hairy eagle.

Elements are pure substances, made from one type of atom. Soda can be broken down into many elements but nitrogen can not be broken down.

Gold, silver, copper, and iron are examples of metals. A gold diamond is shiny because of its metal properties.

Gold conducts heat and electricity. Nickel can be hammered into thin sheets without breaking. Platinum can be pulled into wire.

The helium in my Christmas balloon is a nonmetal. The Oxygen in the air is not shiny because of its nonmetal properties.

A dog cannot conduct electricity. A snap dragon cannot be hammered into thin sheets. A snicker cannot be pulled into wire because they are not metals.

Metalloids have properties of both metals and nonmetals. Silicon is a metalloid that can be found in many materials such as the sand on Lake Tahoe the glass in a vase and certain plastics that make up a favorite toy, car.

Iron is abundant easy to shape when heated and relatively strong.Chemical Property ability of a substance to undergo chemical change• Composition of matter always changes

• Another term for Chemical change• One or more substance change into one or more new substance during chemical reactionReactant a substance present at the start of the reactionProduct substance produced in the reaction

How can you tell whether a chemical change has taken place? transfer in energy change in color production of gas formation of a precipitate

• An atom or a group of atoms that has acquired electric charge by gaining or losing one more electron• Cathode • Anode• Anion• Cation

• Any physical change or chemical reaction, mass is conserved.• Mass is neither created nor destroyed.

• A given compound always shows a fixed proportion.• A chemical compound always contains the same elements in the same percent by mass. • When two elements combine to form a given compound, they always do so in a fixed proportion.

Finding the % of Carbon and Oxygen% C = mass C x 100 % O = mass of O x 100 72.8%

mass of CO2 27.2% mass of CO2

Trial Mass of C (g)

Mass of O2

(g)Mass of CO2

(g)

1 2.00 5.34 7.34

2 15.00 40.05 55.05

3 5.00 13.36 18.36

• When two elements combine to form more than one compound, the masses of one element which combine with a fixed mass of the other element are in a ratio of small whole numbers such as 2:1, 1:1, 2:3, etc.Example C D1st Compound 2.276 0.792 0.348

2nd 1.422 0.948 0.667

A. Mass fixed at C

therefore the formulas of the two compounds are C DCD 1 0.348 = 1 0.348

CD2 1 0.667 = 2

0.348

Folder at the desktop : New Bio lecturesFind the File name: introduction to Biology page 61 (Scientific Measurements)

• Encounter very large or very small numbers.Examples: A single gram of hydrogen, contains approximately 602 000 000 000 hydrogen atoms 6.02 x 10 ? The mass of an atom gold is 0.000 000 000 000 327 gram. 3.27 x 10 ?

A given number is written as the product of two numbers:

a coefficient a 10 raised to a power

Accuracy how close a measurement to the True valuePrecision series of measurement

Accuracy Correct valuePrecision repeated measurements

Accepted value: true valueExperimental value: measured in labFormulaError: experimental value – accepted value

Percent error: _____error_______ x 100 accepted value

Include all the digits that are known, plus a last digit that is estimated. Measurements must always be reported to the correct number of significant figures because calculated answers often depend on the number of significant figures in the values used in the calculation.

1. Every nonzero digit in a reported measurement is assumed to be significant. Ex. 24.7 meters, 0.743 meters and 714 meters each has 3 significant measurement.

2. Zeros appearing between nonzero digits are significant. Examples 7003 meters and 40.79 metes have 4 s.f.

3. Left zeros appearing in front of nonzero digits are not significant. They are just a placeholder. Ex. 0.000 099 meters has 2 s.f. you will write them as 7.1 x 10 -³

4. Zeros at the end of a number and to the right of a decimal point are always significant. Ex. 43.00 meters, 1.010 meters have 4 s.f.

5. Zeros at the right most end of a measurement that lie to the left of an understood decimal point are not significant if they serve as placeholders to show the magnitude of the number. Example 7000 meters and 27210 meters have 1 and 4 s.f respectively.

6. The numbers are all in s.f. if it is exact amount/count for ex. 23 students or 60 mins= 1 hour.

24.7 74.3 512 meters

7.003 1.505 87.29

0.0071 0.043 0.000 0044

9.000 43.00 1.010

300 7000 27210

Calculate the sum of the three measurements. Give the answer to the correct number of significant figures. 12.52 meters + 349.0m + 8.24m Answer: 369.8 or 3.69 x 102 meters

2.10 meters x 0.70 meter = 1.47 (meter)2

Answer: 1.47 (meter)2 = 1.5 meters 2

• Basic unit of length or linear measure is meter

METRIC UNITS OF LENGTHKilometer (km) 1 km = 103 m Length of 5 city

blocks

Meter (m) Base unit Height of doorknob from the floor

Decimeter (dm) 101 dm Diameter of large orange

Centimeter (cm) 102 cm Width of shirt button

Millimeter (mm) 103 mm Thickness of dime

Micrometer (um) 106 um Diameter of bacterial cell

Nanometer (nm) 109 nm Thickness of RNA molecule

Volume is the space occupied by any sample of matter.• Unit being use cubic meter (m3)

Kilogram (kg) is the basic unit of massPlatform balance to measure mass of an object

Metric Units of Mass

Kilogram (kg)

103 g Small textbook

Gram (g) 10-3 kg Dollar bill

Milligram (mg)

103mg = 1 g

Ten grains of salt

Microgram (ug)

106 ug = 1g

Particle of baking powder

• When you hold a glass of hot water the transfer of heat.• Almost all substances expand with an increase in temperature and contract as the temperature decreases. (very important exception is water)•Celsius was named after to Anders Celsius a Swedish astronomer.• Celsius scale sets freezing point of water at 0 degree and the boiling temperature is 100 degree C.• Kelvin, named after to Lord Kelvin a Scottish physicist and mathematician• freezing point 273.15 and the boiling point 373.15 degree C

°F = 9 °C + 32 5

°C = 5 (°F – 32) 9

K = °C + 273 ° C= K - 273

Normal human body temperature is 37 °C. What is the temperature in Kelvin?Given: 37 °CUnknown: KelvinFormula : K = °C + 273Solution: K = 37 °C + 273Answer: K= 310 Correct! It lies between 273K up to 373K

Convert 14 °F to °C and KelvinGiven: 14 °FUnknown: °C and KelvinFormula: °C = 5 (°F – 32) 9

K = °C + 273Solution:Anwers: -10 °C and 263 K

• Energy is the capacity to do work or to produce heat.• Joule (J), named after the English physicist James Prescott Joule and the Calorie (cal) are common units of energy. • One calorie is the quantity of heat that raises the temperature of 1 g of pure water by 1 °CFormula1J = 0.23901 cal = 4.184 J

Calculate the quantity of heat in joules required to raise the temperature of 135 g of water from 11 °C heat to 41 °C.Given : 135 g of water 11 to 41 °CFormula: Heat required = mass x specific heat x temperature change1 cal = 4.184 J/ g °CSolution: 135g x 4.184 J x (41-11 °C) g °C = 1.7 x 104

• Are ratio of equivalent measurements.• Useful in solving problems in which a given measurement is multiplied by a conversion factor, the numerical value is generally changed, but the actual size of the quantity measured remains the same.Example:I meter = 10 decimeters = 100 centimeters = 1000 millimeters

Express 750 dg to gGiven: mass : 750 dg1g = 10 dg or 1g 10 dgSolution: 750 dg x 1g 10 dg

Answer: 75 g

What is 0.073 cm in micrometers?Given: 0.073 cm = 7.3 x 10 -2 cm 10 2 = 1 m 1m = 10 6 umUnknown: umFormula: cm meters micrometersSolution: 7.3 x 10 -2 cm x 1 m x 10 6 um 10 2 1m

Answer: 7.3 x 10 2 um

• Mass per unit volume of a substance• Ratio of the mass of an object to its volume.• Is an intensive property that depends only on the composition of a substance, not on the size of a sample.• Formula: Density = mass volume• Corn oil and corn syrup

Material Density at 20°C (g/cm3)

Material Density at 20°C

Corn oil 0.9222 Helium 0.166

Corn syrup 1.35 – 1.38 Oxygen 1.33

Table sugar 1.59 Carbon Dioxide

1.83

Gold 19.3 Ammonia 0.718

Example :A copper penny has a mass of 3.1 g and a volume of 0.35 cm 3. What is the density of copper?Given:Mass: 3.1 g volume= 0.35 cm3Unknown: density= ?g/cm3Formula: Density = mass = 3.1 g volume 0.35 cm3 = 8.8571 g/cm3 = 8.9 g/cm3 (rounded off to two significant figures)

• Density of a substance generally decreases as its temperature increase

Atom is the smallest particle of an element that retains its identity in a chemical reaction.Democritus (460 B.C.-370 B.C.) is a Greek philosopher was among the first to suggest the existence of atom.• He believed that atoms were indivisible and indestructible.

An English chemist and school teacher responsible for the modern process of discovery regarding atoms.• By using experimental methods, he transformed Democraticus’s ideas on atoms into a scientific theory. All elements are composed of tiny indivisible particles called atoms. Atoms of the same element are identical. Atoms of different elements can physically mix together or can chemically combime in simple whole-number ratios to form compounds. Chemical reactions occur when atoms are separated, joined, or rearranged.

One important change in Dalton’s atomic theory is that atoms are now known to be divisible. They can be broken down into even smaller, more fundamental particles called subatomic.Three kinds of Subatomic Particles:• Electrons• Protons• Neutrons

ELECTRONS• Negatively charged subatomic

particles.• Thomson performed

experiments that involved passing electric current

through gases at low pressure.• Travels from cathode (-) to

anode (+)• Thomson examine two ways

that a cathode ray can be deflected by using magnet and by using electrically charged plates.

• A positively charged plate attracts the cathode ray, while negatively charged plate repels it.•Thomson knew that opposite charges attract and like charges repel, so he hypothesized that a cathode ray is a stream of negatively charged particles moving at high speed.• He called these particles corpuscles, later named electrons. He concluded that electrons must be parts of the atoms of the elements.• US physicist Robert Millikan carried out experiments to find the quantity of charged carried by an electron.• He is the one responsible for charge and mass.

•

Positively charged subatomic particles.• Example is a hydrogen atom (lightest kind of atom) loses an electron, what is left?• Eugen Goldstein (1850-1930) a German Physicist observed a cathode-ray-tube and found rays travelling in the direction opposite of that cathode rays.• He called that canal rays and concluded that they were composed of positive particles.

• No charge but with a mass nearly equal to that of a proton• James Chadwick (1891-1974) an English Physicist confirmed its existence

Particle Symbol

RelativeCharge

Relative mass(mass of proton= 1)

Actual mass(g)

Electron e - 1 - 1/1840 9.1 x 10 -28

Proton p+ 1 + 1 1.67 x 10 -24

Neutron n o 0 1 1.67 x 10 -24

• He concluded that all the positive charge and almost all the mass are concentrated in a small region that has enough positive charge to account.• He called this region as Nucleus.• He said that a nucleus is a tiny central core of an tom and is composed of proton and neutrons.• Rutherford atomic model is known as the nuclear atom.• In nuclear atom, the protons and electrons are located in the nucleus.• While the Electrons are distributed around the nucleus and occupy almost all of the volume of atom.

• of an element is the number of protons in the nucleus of an atom of that element.• Elements are different because they contain different number of protons.

Name Symbol Atomic # Protons Neutron Mass # # of Electrons

Hydrogen

H 1 1 0 1 1

Helium He 2 2 2 4 2

Lithium Li 3 3 4 7 3

Beryllium

Be 4 4 5 9 4

Boron B 5 5 6 11 5

Carbon C 6 6 6 12 6

Nitrogen N 7 7 7 14 7

Oxygen O 8 8 8 16 8

Fluorine F 9 9 10 19 9

Neon Ne 10 10 10 20 10

• Total number of protons and neutrons in an atom• Example a helium atom has 2 protons and 2 neutrons so its mass is 4.• The number of neutrons in an atom is the difference between the mass number and atomic number.• Number of neutron = mass number – atomic number

How many protons, electrons and neutrons are in each atom? Atomic number Mass Number

Beryllium (Be) 4 9

Neon (Ne) 10 20

Sodium 11 23

are atoms that have the same number of protons but different neutrons. Because isotopes of an element have different numbers of neutrons, they also have different mass numbers. Have an identical numbers of protons and electrons

• Hydrogen has a mass number of 1 and is called hydrogen -1• second isotope has one neutron and a mass number of 2 or a hydrogen -2 or deuterium.• third isotope has 2 neutrons and a mass number of 3, or hydrogen -3 or tritium.• Remember mass number superscript; atomic number subscript

Example is Carbon -12, This isotope of a carbon was assigned a mass exactly of 12 atomic mass units.• AMU is defined as one-twelfth of the mass of a carbon -12 atom. Using these units, a helium -4 atom with a mass of 4.0026 amu, has about one-third the mass of a carbon -12.• While a nickel -60 atom has about 5 times the mass of a carbon -12 atom.• Atomic Mass of an element is a weighted average mass of the atoms in a naturally occurring sample of the element.

Name Symbol Natural Percent Abundance

Mass (amu) Average atomic mass

Hydrogen ₁¹H

₁²H

99.985

0.015

1.0078

2.0141 1.0079

Helium ³He2

4He2

0.0001

99.9999

3.0160

4.00264.0026

Calculate the atomic mass of Hydrogen

(To calculate: multiply the mass of each isotope by its natural abundance, express as a decimal, and then add the products.)

Given:

1 H 2 H

Mass (amu) = 1.0078 Mass (amu) = 2.0141

Nat’l % A = 99.985 Nat’l % A = 0.015

Formula: Average atomic mass =

(amu) (Nat’l %) + (amu) (Nat’l %)

Isotope = 10 X

Mass (amu) = 10.012

Natural percent abundance = 19.91% = 0.1991

AMU = ?

Isotope = 11 X

Mass (amu) = 11.009

Natural percent abundance = 80.09% = 0.8009

AMU = ?

10.012 amu x 0.1991 = 1.993 amu

11.009 amu x 0.8009 = 8.817 amu

Answer = 10.810 amu

Given:

Isotope 1 Isotope 2

1 Helium 2 Helium

Mass (amu) = 3.0160 amu Mass (amu) = 4.0026 amu

Nat’l % A = 0.0001 Nat’l % A = 99.9999

Isotope 1 Isotope 2

63 Copper 65 Copper

Mass (amu) = 62.93 amu Mass (amu) = 64.93 amu

Nat’l % A = 69.2% Nat’l % A = 30.8%

Name # Natural Percent Abundance

Mass(amu)

Carbon 12

98.891.11

12.00013.003

Nitrogen 1 2

99.630.37

14.00315.000

Oxygen 1 2

99.7590.037

15.99516.995

Sulfur 1 2

95.0020.76

31.97232.971

Chlorine 1 2

75.7724.23

34.96936.966

Name # Natural Percent Abundance

Mass(amu)

Bromine 12

50.69%49.31%

78.9280.92

Boron 12

20.0 %80.0%

10.0111.01

Lithium 67

7.5%92.5%

6.0151227.016003

Iron 5456

5.845%91.754%

53.939655.9349

Copper 6365

69.17%30.83%

62.929664.92779

• An arrangement of elements in which the elements are separated into groups based on a set of repeating properties.• Allows you to easily compare the rpoperties of one element (or group of elements) to another element.

•Notice that the elements are listed in order of increasing atomic number, from left to right and top to bottom.

•Each horizontal row of the periodic table is called a PERIOD.•Each vertical row of the periodic table is called a GROUP.

Niels Bohr a young Danish Physicist, said that Rutherford’s model need to be improved. He proposed that an electron is found only in specific circular paths,

or orbits, around the nucleus..

Energy levels these are the fixed energies within the electron

Quantum of energy is the amount of energy required to move an electron from one energy level to another energy level. The energy of one electron is said to be quantitized.

It determines the allowed energies an electron can have how likely it is to find the electron in various locations around the nucleus.

Erwin Schrodinger an Australian physicist used new results to devise and solve a mathematical equation describing the behavior of the electron in a hydrogen atom.

It is the probability of finding an electron at various location around nucleus. is often thought of as a region of space in which there is a high probability of finding an electron. The energy levels of electrons in the quantum numbers (n). Each energy sublevel corresponds to an orbital of a different shape, which describes where the electron is likely to be found.

Principal Energy Level

Number of Sublevels

Type of Sublevel

n = 1 1

1 S (1 orbital)

n = 2 2

2 s (1 orbital), 2p (3 orbitals)

n = 3 3

3 s (1 orbital), 3p (3 orbitals), 3d (5 orbitals)

n = 4 4

4 s (1 orbital), 4 p (3 orbitals),4 d (5 orbitals), 4 f (7 orbitals)

Electrons occupy the orbitals of lowest energy first.

Table 3-6a - Orbital and Electron Capacity for the Four Named

Sublevels

Sublevel # of orbitalsMaximum number of electrons

s 1 2

p 3 6

d 5 10

f 7 14

According to Pauli, an atomic orbital may describe at most two electrons.

Ex. Either 1 or 2 electrons can occupy s or p orbitals

states that electron occupy orbitals of the same energy in a way that makes the number of electrons with the same spin of direction as alarge as possible.

Classical mechanics adequately describes the motions of bodies much larger than atoms, while quantum mechanics describes the motions of subatomic particles and atoms as waves.

Periodic comes from the Greek roots peri meaning “around” and hodos, meaning “path”.

In a periodic table, properties repeat from left to right across each period.

The Greek word metron means “measure”

What does perimeter mean?

A Russian chemist and a teacher published a table of the elements.

Mendeleev arranged the elements in the periodic table in order of increasing atomic mass.

Henry Moseley 1913, British determined atomic number for each known element.

Elements are arranged in order of increasing atomic number.

Periodic Law When elements are arranged in order of increasing atomic number, there is a periodic repetition of their physical and chemical properties.

Sodium printed in black because it is solid in room temperature.

Symbol for gases are in red.

Symbol for two elements that are liquids at room temperature, mercury and bromine are color blue.

Are used to distinguish groups of elements.

Two shades of gold are used for metals in Group 1A and 2A.

Group 1A alkali metals

Group 2A alkaline earth metals

“alkali” Arabic word al aqali means the ‘ashes’

Wood ashes are rich in the alkali metals sodium and potassium.

Nonmetal of Group 7A (nonmetals) are called halogens, comes from the Greek word hals, meaning “salt”, and a Latin word genesis, means “to be born”

There is a general class of compounds called salts, which include the compound called table salt.

Chlorine, Bromine and Iodine the most common halogens, can be prepared from the salts.

Electrons play a key role in determining the properties of elements. So there should be a connection between an element’s electron configuration and its location in the periodic table.

Elements can be sorted into noble gases, representative elements, transition metals

These are the elements in Group 8A.

These nonmetals are sometimes called the inert gases because they rarely take part in a reaction.

Helium (He) 1s2

Neon (Ne) 1s 2 2s 2 2p6

Argon (Ar) 1s 2 2s 2 2p6 3s2 3p6

Krypton (Kr) 1s 2 2s 2 2p6 3s2 3p6 3d10 4s2 4p6

Because they display a wide range of physical and chemical properties. Some are metals… Most of tem are solids, but a few are gases at room temperature, and one, bromine, is a liquid.

Lithium (Li) 1s 2 2s 1

Sodium (Na) 1s 2 2s 2 2p6 3s1

Potassium (K) 1s 2 2s 2 2p6 3s2 3p6 4s1

In atoms of Carbon, Silicon, Germanium in Group 4A, there are four electrons in the highest occupied energy level.

Carbon (C) 1s 2 2s 2 2p2

Silicon (Si) 1s 2 2s 2 2p6 3s2 3p2

Germanium (Ge) 1s 2 2s 2 2p6 3s2 3p6 3d10 4s2 4p2

It means the Elements in the B groups, which provide a connection between the two sets of representative elements.

Two types of transition elements

1. Transitional metal

2.Inner Transitional metal

These are the Group B elements that are usually displayed in the main body of a periodic table. Ex. Copper, silver, gold, and iron.

In atoms here, the highest occupied s sublevel and a nearby d sublevel contain electrons. These elements are characterized by the presence of electrons in d orbitals.

It appear below the main body of the periodic table. In atoms of an inner transition metal, the highest occupied s sublevel and a nearby f sublevel generally contain electrons.

The inner transition metals are characterized by f orbitals that contain electrons.

It is the energy required to remove an electron from an atom.

First ionization energy tends to decrease from top to bottom within a group and increase from left to right across a period.

During reactions between metal and nonmetals, metal atoms tend to lose electrons and nonmetal atom tend to gain electrons. The transfer has a predictable affect on the size of the ions that form.

Cations are always smaller than the atoms from which they form. Anions are always larger than atoms from which they form.

It is the ability of an atom of an element to attract electrons when the atom is in a compound. Scientists use such factors such as ionization energy to calculate values for electronegativity.

Linus Pauling won a Nobel Prize in Chemistry for his work on chemical bonds. He was the first to define electronegativity.

Electronegativity values decrease from top to bottom within a group.

For representative elements, the values tend to increase from left to right across a period.

Metals at the far left of the far left of the periodic table have low values. By contrast, nonmetals at the far right (excluding noble gases) have high values.

Example:

Least is Cesium, has least tendency to attract electrons.

Most electronegative is Flourine, has strong tendency to attract electrons.

Atomic size decreases

Ionization energy increases

Electronegativity increases

Nuclear charge increases

Shielding is constant

Atomic size increases

Ionic size increases

Ionization energy decreases

Electronegativity decreases

Nuclear charge increases

Shielding increases

Are the electrons in the highest occupied energy level of an element’s atoms. The number of valence electrons largely determines the chemical properties of an element.

The number of valence electron is related to the group numbers in the periodic table.

To find the number of the valence electrons in an atom of a representative element, simply look at its group number.

Except for the noble gases (Group 8A); wherein Helium has 2 valence electron.

Are usually only the electrons used in chemical bonds. Therefore as a general rule, only the valence electrons are shown in electron dot structures.

Electron Dot Structures are diagrams that show valence electrons as dots.

Octet Greek word okto meaning eight. Like in the electron.

Gilbert Lewis used this fact to explain why atoms form certain kinds of ions and molecules. He called this octet rule.

In forming compounds, atoms tend to achieve the electron configuration of a noble gas. Just like the electrons in highest energy level ns2 np6.

Atoms of the metallic elements tend to lose their valence electrons, leaving a complete octet in the next-lowest energy level.

Atoms of some nonmetallic elements tend to gain electrons or to share electrons with another nonmetallic element to achieve a complete octet.

Atom is electrically neutral = number of protons and electrons.

Therefore, an ion forms when an atom or group of atoms loses or gains electrons.

An atom’s loss of valence electrons produces a cation, or a positively charged ion.

Example: sodium atom forms a sodium cation.

Similar in in their names but different chemically.

-e –

Na 1s2 2s2 2p6 3s1 Na + 1s2 2s2 2p6

Sodium Atom Sodium ion Neon

atom

. .

Na . Na + : Ne :

. .

Ionization Na. Na + + e -

Magnesium Group 2A

Mg Mg 2+ + 2e

Atom of Iron / Fe may lose 2 or 3 electrons = Fe 2+ or

Fe 3+

There is an exception like silver atom would have to lose 11 electrons. They don’t have noble-gas electron configuration.

Anion is an atom or a group of atoms with a negative charge.

The gain of negatively charged electrons by a neutral atom produces an anion.

The name of anion typically ends in –ide.

Chlorine atom (Cl) forms a chloride ion (Cl -)

Oxygen atom (O) forms an oxide ion (O2-)

Because they have relatively full valence shells, atoms of nonmetallic elements attain noble-gas electron configuration more easily by gaining electrons than by losing them.

Ex. Chlorine belongs to Group 7A (the halogen family)

+e

Cl 1s2 2s2 2p6 3s2 3p5 Cl - 1s2 2s2 2p6 3s2 3p6

Notice that it has the same electron configuration as the noble gas argon.

Chlorine atom Chloride ion Argon atom

7dots 8 dots with negative 8 dots

The ions that are produced when atoms of chlorine and other halogens gain electrons are called halide ions.

All halogen atoms have seven valence electron to achieve the electron configuration of noble gases. (F, Cl, Br, & I)

Oxygen atoms attain the electron configuration of neon by gaining two electrons.

Oxygen atom Oxide ion Neon atom

.. .. ..

: O. :O: 2- :Ne:

. .. ..

O + 2e O2-

Compounds composed of cations and anions. Ionic compounds are usually composed of metal cations and nonmetal anions.

Anions and cations have opposite charges and attract one another by means of electrostatic forces. The electrostatic forces that hol ions together in ionic compounds are called Ionic bonds.

Ex. Sodium cations and chloride anions

It shows the kinds and numbers of atoms in the smallest representative unit of a substance.

Chemical formula is the lowest whole-number ratio of ions in an ionic compound. Ex. Is NaCl one Na+ to each Cl- )

Another is Magnesium chloride contains Magnesium cations (Mg2+) and chloride anions (Cl-) Its ratio 1:2 so the formula unit is MgCl2.

crystalline solids at room temperature

generally have high melting points

can conduct an electric current when melted or

dissolved in water.

The coordination number of an ion is the number of ions of opposite charge that surround the ion in a crystal.

The valence electrons of metal atoms can be modeled as a sea of electrons. That is the valence electrons are mobile and can drift freely from one part of the metal to another.

Metallic bonds consist of the attraction of the free-floating valence electrons for the positively charged metal ions.

Are mixture composed of two or more elements, at least one of which is a metal. Ex. Brass, an alloy of copper and zinc.

Alloys are important because their properties are often superior to those of their component elements.

Covalent bond is the atoms held together by sharing electrons.

Molecule is a neutral group of atoms joined together by covalent bonds.

Diatomic molecule is a molecule consisting of two atoms. Ex. Oxygen molecule

Molecular compound is a compound composed of molecule Ex. Water and Carbon monoxide (CO).

compounds tend to have relatively lower melting and boiling points than ionic compounds.

A molecular formula is the chemical formula of a molecular compound.

It shows how many atoms of each element a molecule contains.

it reflects the actual number of atoms in each molecule.

it describes molecules consisting of 1 element It doesn’t tell you about a molecules structure.

In forming covalent bonds, electron sharing usually occurs so that atoms attain the electron configuration of noble gases.

Two atoms held together by sharing pair of electrons are joined by a single covalent bond

Ex. H. + .H H:H

hydrogen hydrogen hydrogen

atom atom molecule