Bonding & Chemical NomenclatureChapter 8 & 9

Some Key Terms

1. Chemical bond – a mutual electrical attraction b/w the nuclei and valence electrons of different atoms that binds the atoms together.

2. Ionic Bond – the electrostatic attraction of oppositely charged particles (cations & anions)

3. Ionic Compound – Molecules that contain ionic bonds where the positive and negative charges are equal.

4. Metallic bonding – chemical bond that results from the attraction b/w metal atoms and the surrounding sea of electrons

Key Terms cont.

5. Covalent bond – results from the sharing of electrons

6. Molecular compound – molecules that contain covalent bonds and whose simplest units are molecules.

7. Chemical Formula – a formula that indicates the relative #’s of atoms of each kind in a chemical compound. Uses atomic symbols and numerical subscripts. Ex. NaCl, Mg(OH)2

8. Polyatomic Ion – A charged group of covalently bonded atoms. Contains two or more different elements

Key Terms cont.

9. Molecule – Neutral group of atoms held together by covalent bonds.

10. Oxidation number - # assigned to an atom in a molecular compound or ion that indicates its distribution of electrons (charge)

11. Binary Compound – A compound composed of 2 different elements

12. Octet rule – Chemical compounds tend to form so that each atom has an octet (8) electrons in the highest energy level except for a few of the smallest atoms.

What are ions?

• Ions are atoms that have lost or gained electrons to become positively or negatively charged.

• Metals tend to form positively charged ions called cations

• Nonmetals tend to form negatively charged ions called anions.

• To determine the charge of an ion we must look at the arrangement of VALENCE ELECTRONS.

Review of Lewis Dot Diagrams

• Lewis dot diagrams show an elements valence electrons as dots around the element’s symbol.

• To determine valence electrons for main group elements refer to the “A” group number.

• REMEMBER – a valence electron is an electron in the outermost energy level

Formation of Ions• Label your periodic table with the following

GENERAL charges above each group:• Group 1A = +1• Group 2A = +2• Group 3A = +3• Group 4A = +/-4• Group 5A = -3• Group 6A = -2• Group 7A = -1• Group 8A = 0

Writing Ionic Formulas

• CRISS-CROSS• Look up the charge for the first element, then look up the

charge for the second element or group (polyatomic ion) and then criss-cross to get the subcripts

• If the charges are equal and opposite they cancel and no criss-cross is needed.

• Examples:– Sodium chloride– Potassium sulfide– Magnesium phosphate

Naming Binary IonicInvolves a metal and a nonmetal• Name the metal• Name the nonmetal and change the

ending to –ide.

ExamplesNaCl

K2O

BaF2

Naming Binary Ionic with transition metals

1. Name the metal

2. Using a roman numeral write the oxidation number of the metal in parenthesis. To get the oxidation number uncriss-cross the charges.

3. Name the nonmetal and change the ending to –ide

Examples

CuBr2

Fe2O3

Still Metal – Nonmetal. We use this method only if the metal can have a variable charge/oxidation number. The majority of these will be transition metals. Exceptions to memorize: Silver (Ag+1), cadmium (Cd+2), zinc (Zn+2)

Naming Ionic Compounds with Polyatomic Ions

1. Name the metal 2. Name the polyatomic ion3. Be sure to use a roman numeral if it is

necessary (transition metals)

Examples

LiNO3

KMnO4

Na2CO3

Naming Binary Molecular (covalent) Compounds

Involves a bond b/w 2 nonmetals1. Name the 1st nonmetal. Use a prefix if there is

more than one.2. Name the 2nd nonmetal ALWAYS use a prefix.

Change the ending to –ide.

ExamplesNO

P2O5

SO3

Prefixes

1 mono- 6 hexa-

2 di- 7 hepta-

3 tri- 8 octa-

4 tetra- 9 nona-

5 penta- 10 deca-

Writing Formulas for Molecular Compounds

• Write the symbol for each of the elements involved• Look at the prefixes and decide what numbers are being

represented.• Write those numbers as subscripts to the right of the

elements symbol in the formula• Examples:

– sulfur trioxide– Carbon monoxide– Dinitrogen monoxide

Naming Binary Acids

• Acids generally start with Hydrogen

1.Binary Acids (H with one element)– Use the prefix hydro-– Then add the name of the second element

and change the ending to –ic acid– HCl hydrochloric acid– HBr hydrobromic acid– HI hydroiodic acid

Naming Acids with Polyatomic Ions

• Hydrogen with a polyatomic ion (group of atoms with a charge)– Identify the polyatomic ion– Change the ending accordingly:

• -ate to –ic acid• -ite to -ous acid• (Do NOT use the prefix Hydro-)

• H2SO4 sulfuric acid

• HNO3 nitric acid

• HNO2 nitrous acid

Writing Formulas for Acids

• For acids you must look up the charges of the ions invovled.

• Hydrogen is the first element – look up its charge• Then if it is a hydro- prefix acid look up the second

element and charge and criss-cross• If it is an –ic acid or and –ous acid, you must look up the

polyatomic ion and its charge then criss-cross

• Example:– Hydrobromic acid– Sulfuric acid

Naming simple bases

• Common bases for us will end in –OH or hydroxide ion

• So name the first element then name the hydroxide

– NaOH sodium hydroxide