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The valence electrons in an atom have HIGH POTENTIAL ENERGY

By bonding with other atoms, potential energy is decreased creating

stable compounds.

Symbols of atoms with dots to represent the valence-shell

electrons. (The valence- are the e- directly involved in

bonding).

Ar Mg

C

The Noble Gases do not react with other elements because they are already

STABLE.The outer most “s” and “p” orbitals are completely filled with 8

electrons, satisfying the octet rule.

Ne

Elements combine with each other to achieve noble gas electron configurations

or(8 outer e-)

**The exceptions to the octet rule are Hydrogen and Helium

(they only need 2)

• The forming of chemical compounds results in chemical change.

• Compounds are made up of chemically united elements

• Compounds have completely different characteristics than its

component elements• Compounds are NEUTRAL

2H2O = H2O = HHO H2O HHO

Subscript = # of atomsCoefficient = # of molecules

N: 1H: 5O: 1

The Gaining and Losing of Electrons

to form IONS. (An ion is an atom with a charge.)

sharing of electrons

• Soluble in water• Do not transmit electric current• Brittle • High melting and boiling points

Ionization Energy: the amount of energy needed to remove an e- from

an atom. Nonmetals have

high ionization

energy because they are closer to satisfying the octet

rule!

Metals have a

low ionization

energy

the higher the electronegativity the greater the ability to pull electron to itself

The nature of a bond is determined by differences in electronegativity. The GREATER the electronegativity difference, the MORE ionic the bonding.

Ionic compounds result when metals react with nonmetals

• Metals lose electrons to achieve a stable outer energy level

• Positive ions form when electrons are given away

Group 1 metals ion 1+

Group 2 metals ion 2+

Group 13 metals ion 3+

1. Write the symbol for the cation (+) followed by the symbol for the anion (-).

2. Put any polyatomic ions (see green boxes) in parenthesis

3. Write the oxidation numbers above the appropriate ions

4. Use the criss-cross method to deterimine # of atoms (do not criss-cross ones)

5. Make sure the sum of all ox# is ZERO.6. Reduce

Na – e Na +

Sodium Atom

Sodium Ion

11 p+11 e-

0

11 p+10 e-

1+

+ e 1-

Fluoride Atom

Fluoride Ion

17 p+17 e-

0

17 p+18e-

1-

Na + Na1+ 1-

YOUR TURN…

Using dot diagrams, draw the Lewis structures that result when the following elements form ionic bonds:

A. Potassium + chlorine

B. Magnesium + fluorine

Potassium + Chlorine

Magnesium + Fluorine

K Cl K Cl+

FMg + F FMg

Oxidation: the process of losing electrons

▪ Creates an ion with a + charge▪ Creates cations

Reduction: the process of gaining electrons

▪ Creates an ion with a – charge▪ Creates anions

1. Write the name of the cation (+)2. Write the name of the anion (-) with an

ide suffix

NaClSodium and Chlorine

Sodium Chloride

The oxidation number is not always the same, it varies.

The variable oxidation states are represented with a roman numeral in

parentheses and are located in groups 3-12 on the periodic chart.

Copper Copper (I) = Cu+ Copper (II) = Cu2+

Write the symbol for the cation followed by the symbol for the anion.

Write the oxidation numbers above the appropriate ions.

Criss-CrossCopper(III) Oxide: CuO Cu2O3

Copper(I) Oxide: CuO Cu2O

3+ 2-

1+ 2-

SO4 Sulfate 2-C2H302Acetate 1-NO3 Nitrate 1-NO2 Nitrite 1-NH4 Ammonium 1+HCO3 Bicarbonate 1-CO3 Carbonate 2-OH Hydroxide1-ClO3 Chlorate 1-PO4 Phosphate 3-

1. Write the name of the cation (+)2. Write the name of the anion (-)3. If either is a polyatomic ion write the

name of the polyatomic ion (you don’t need to change any suffixes)

Na(OH)Sodium Hydroxide

Write the symbol for the cation followed by the symbol for the anion.

Put all polyatomic ions in parentheses!! Write the oxidation numbers above the

appropriate ions. Criss-CrossCalcium Phosphate: Ca(PO4) Ca3(PO4)2

Ammonium Phosphate: (NH4)(PO4) (NH4)3(PO4)

2+ 3 -

1+ 3 -

Cu(OH) Copper (I) Hydroxide

Ni2O3 Nickel (III) Oxide

1- = 01+

2-6- =03+

sharing of electrons

Between nonmetallic elements of similar electronegativity.

Formed by sharing electron pairsStable non-ionizing particles, they

are not conductors at any stateExamples; O2, CO2, C2H6, H2O, SiC

Water is a polar molecule because oxygen is more electronegative than hydrogen, and therefore electrons are pulled closer to oxygen.

A polar molecule has a (+) and a (-) end.

A nonpolar molecule does not have charged ends.

Metal  +  Nonmetal  -->  ionic compound (usually)

Metal  +  Polyatomic ion  —>  ionic compound (usually)

Nonmetal  +  Nonmetal  —>  covalent compound (usually)

Hydrogen  +  Nonmetal  —>  covalent compound (usually)

The chemical symbol for the atom is surrounded by a number of dots corresponding to the number of valence electrons

1. Write the name of the cation (+) with appropriate prefix (do NOT use mono for the cation)

2. Write the name of the anion (-) with the appropriate prefix

CO2

Carbon Dioxide

1: mono2: di3: tri4: tetra5: penta6: hexa

Formula weight is the sum of the atomic masses.

Example- CO2Mass, C + O + O

12.011 + 15.994 + 15.99443.999