Ionic and Covalent Bonding

Chapter 8/9

Chemical Formula

• Indicates the composition of a compound and the # of atoms in one molecule of an element

• Molecule – smallest particle of a substance that retains the composition and properties of that substance

Two Types of Molecules

• Monatomic Molecule – each molecule consists of a single atom– Ex: Ne, Ar and Ca

Diatomic Molecule – each molecule contains 2 atoms- there are seven diatomic molecules- H2, O2, N2, Cl2, F2, Br2, I2

Major Classes of Compounds

• Ionic Compounds – metal and a nonmetal bonded together

• Molecular Compounds – two or more nonmetals bonded together

Examples

• CaCl2 -

• SO2 –

• BaO –

• CCl4 -

Atomic StructureCharge

Symbol Mass Location

Proton

Electron

Neutron

Atomic Structure (cont’d)

Atomic Number – Whole number on the periodic table- tells us the number of p+

- tells us the number of e- in the neutral state

Ex: C has _________ p+ and e-

Atomic Structure (cont’d)

Atomic Mass - the average mass of an atom- tells us the number of pt and n0 together

Therefore:# of neutrons = atomic mass – atomic number

Ionic Substances

• 1) A metal combines with a nonmetal

• 2) Electrons are transferred from the metal to the nonmetal

• 3)Elements no longer have a net charge of zero

• 4) Ions – (charged particles) are formed

Ionic Substances

• An element in an uncombined state has equal numbers of protons and electrons.

• Ex: Na 11 p+ Cl 17 p+

11 e- 17 e-

0 charge 0 charge

Lose Electron

• 1) Typically metals

• 2) Atom now has more p+ than e-

• 3) An overall + charge

• 4) “Cation”

Gain Electron

• 1) Typically a nonmetal

• 2) Atom now has more e- than p+

• 3) An overall – charge

• 4) “anion”

Na + Cl NaCl

• 1) each Na atom loses one e-– Na now has 11 p+ and 10 e- net charge

+1

2) each Cl atom gains one e-- Cl now has 17 p+ and 18 e- net charge -1

*** the attraction between the + ion and the – ion is what allows the bond to form

Group #

Element

e- config.

Dot Diagram

# of valence e-

Gain or lose e- ?

How many?

Charge of the ion

1

2

13

14

15

16

17

18

Predicting Formulas of Ionic Compounds

• The total net charge in an Ionic Compound MUST be ZERO

• Ex: Mg and F

Rules for Writing Formulas of Ionic Compounds

1) Write the symbols for the two elementsEx: Cation (Metal) always comes first

2) Determine the charge of each element

3) Determine the subscripts of each elementRemember – the net charge must equal zero

Polyatomic Ions

• Groups of atoms of more than one element that carry a charge– Act as a single ion– Do not usually break up during a

chemical rxn

– Sulfate – SO4 -2

List of Polyatomic Ions

• The sooner you learn them – the better!!!!!

The formula of the ion is placed in parentheses and the subscript is placed outside the parenthesesex: Al +3 and SO4 -2

Al2(SO4)3

Write the correct formulas for:

• Ba and Cl

• Li and S

• Sr and PO4 -3

• NH4 +1 and S

• Al and S

Naming Ionic Compounds

Binary Compounds – compounds made up of two elements- name of cation stays the same- name of anion – ending changes to –ide

Ex: NaCl – sodium chloride

Naming Ionic Compounds (cont’d)

Ternary Compounds – compounds made up of three or more elements

- usually include a polyatomic ion - both ion names stay the same

Ex: MgSO4 - magnesium sulfate

** Exception – when NH4 +1 bonds with a single element (ex: NH4 +1 and O) the ending changes to -ide

Metals with more than 1 charge

• Copper + 1 and +2• Lead +2 and +4• Iron +2 and +3• Tin +2 and +4

Stock System

• CuCl2 vs. CuCl

• Both compounds CAN NOT be named Copper Chloride – we need some way of distinguishing between the two

Stock System

• Name of metal is followed by a Roman Numeral which indicates the charge of the cation *** look at previous example

Traditional System

● Uses suffixes at the end of the metals Latin root

● Smaller of the two ions receives suffix of

– ous● Larger of the two ions receives

suffix of -ic

Traditional System

Fe +2 ferrous Pb +2 plumbous

Fe +3 ferric Pb +4 plumbic

Cu +1 cuprous Sn +2 StannousCu +2 cupric Sn +4 Stannic

Formulas of Molecular Compounds

• Molecular Compounds – made up of molecules rather than ions– 2 or more nonmetals bonded through

the sharing of electrons

Oxidation #

• Apparent charge of an atom as it attracts or repels e- from another atom

• Oxygen typically has a -2 oxidation #

Example

N2O nitrogen (II) oxide N = +1

NO nitrogen ( ) oxide N =

N2O3 nitrogen ( ) oxide N =

NO2 nitrogen ( ) oxide N =

N2O5 nitrogen ( ) oxide N =

Traditional System

• Uses prefixes to indicate subscripts on each atom

Subscript Prefix ** Mono is never used with the 1 Mono 1st element in the name of the 2 di compound (ex: CO and CO2)

3 tri4 tetra5 penta6 hexa7 hepta8 octa