formula unit

Covalent Bonding:

Learning to Cooperate

• describe a covalent bond • state the differences covalent and ionic bonds• explain the term molecule • describe a diatomic molecule

Key Wordscovalent compoundcovalent bonddiatomic molecule

Covalent Compound:

Contains two or more NON-METAL atoms.

Formed by SHARING valence electrons to fill outer shell – octet rule.

· A molecule is the smallest unit of a covalent compound.

Non-metal + Non-metal = covalent bonding

Fluorine atom:9 p+

9 e-

F

Fluorine atom:9 p+

9 e-

F

F2

covalent compound

HH

Water H2O

1p

8p1p

O

A molecule has different properties than the atoms from which it is formed

Methane CH4

C

H

H

H

H

Ammonia NH3

NH

H

H

O

Atoms can share one pair of electrons, or two or three pairs.

S

In the end – electrons must be arranged so that each atom has 8 electrons around it.

Diatomic ElementsForming a Covalent Bond with Yourself

No new substance is formed - the covalent bond forms a molecule of only one type of atom.

Diatomic elements are unstable as single atoms.

HH

They form covalent bonds with a same atom to make a stable molecule.

H2

molecule

I H N Br O Cl F ave o ight r ever riends

Diatomic Elements:

2 2 2 2 2 2 2

Element Symbol Diatomic MoleculeIodine I I2 (solid)

Hydrogen H H2 (gas)

Nitrogen N N2 (gas)

Bromine Br Br2 (liquid)

Oxygen O O2 (gas)

Chlorine Cl Cl2 (gas)

Fluorine F F2 (gas)

OOO2

molecule (double bond)

F2

molecule(single bond)

FF

Covalent Bonding:

Naming and Writing

Same – covalent compounds are also named using the “ide” ending for last non-metal.

Different – covalent naming uses prefixes before the name of each element.

Prefixes show the number of atoms of that element in the formula for the molecule.

Diatomic Elements2

Prefix Number of Atoms

mono

1

di 2

tri 3

tetra 4

penta 5

hexa 6

Step 1: first non-metal is named with a prefix to show the number of atoms.

We do not use “mono” for the first non-metal.

nitrogen oxide

N O

Step 2: second non-metal is named with a prefix AND with the “ide” ending.

di

2 4

tetradinitrogen tetroxide

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

sulfur oxide

SO

mono

3

trisulfur trioxide

carbon bromide

C Br

tri

3 6

hexa

tricarbon hexabromide

Writing formulas

Step 1: Write the symbol of each element.

Step 2: Use a subscript to show the number of each type of atom given by the prefix.

Do not reduce covalent formulas.

phosphorus oxide

P O di

2 5

penta

PrefixNumber of

Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6

nitrogen iodide

N I 3

triPrefix

Number of Atoms

mono 1

di 2

tri 3

tetra 4

penta 5

hexa 6carbon oxide

CO 2

di

silicon sulfide

Si S di

2 4

tetra

**Always identify a compound as ionic (m + nm) or covalent (nm + nm) before doing anything.

Prefixes are used in naming covalent compounds ONLY.

Criss-crossing is only used in ionic compounds.

DO NOT reduce covalent compounds.

IMPORTANT POINTS:

sulfur chlorideberyllium chloride

BeCl 2

Be

SCl

mono

2

di

metal non-metal non-metal non-metal

ionic covalent

Cl

Cl

+2

-

-

SCl

Cl