NomenclatureMolecular

Compounds

Recap

• Learned about polyatomic ions• Learned how to name ionic compounds

containing polyatomic ions• Learned how to write chemical formulas for

ionic compounds containing polyatomic ions

Naming Polyatomic Ions

Base polyatomic ion sulphateSO4

2-

Add an oxygen persulphateSO5

2-

Remove an oxygen sulphiteSO3

2-

Remove two oxygen hyposulphiteSO2

2-

Add a hydrogen hydrogen sulphateHSO4

-

Replace one oxygen with sulphur

thiosulphate S2O32-

Learning Goals

• We are learning to…– Name molecular compounds– Write the formula for molecular compounds when

given the name

Molecules

Recall• A molecule is a combination of two or more

non-metal atoms held together by covalent bonds.

• A covalent bond is a connection between non-metal atoms where two atoms SHARE a pair of electrons.

Diatomic Elements

Recall• There are seven diatomic elements they are– Hydrogen: H2

– Nitrogen: N2

– Oxygen: O2

– Fluorine: F2

– Chlorine: Cl2

– Bromine: Br2

– Iodine: I2

• These elements only exist as diatomic molecular elements.

Naming Binary Molecular Compounds

• Binary compounds contain two elements. • The more electropositive atom is written first

and the more electronegative element is written last with an -ide suffix.

• The names of binary molecular compounds use prefixes to indicate how many atoms of each element are in the compound.

Naming Binary Molecular Compounds

Number of Atoms

Prefix Number of Atoms

Prefix

1 mono- 6 hexa-

2 di- 7 septa-

3 tri- 8 octa-

4 tetra- 9 nona-

5 penta- 10 deca-

Naming Binary Molecular Compounds

Note: • The prefix “mono-” is not used when the first

element is only one atom. • Prefixes can be shortened when the ending

vowel of the prefix "conflicts" with a starting vowel in the compound.

• ie: CO is carbon monoxide• ie: P2O5 is named diphosphorus pentoxide.

Naming Binary Molecular Compounds

• Example: Write the name for N2S3 1. Name the first element2. Name the second element, which ends with

“ide” 3. Add prefixes indicating the numbers of atoms

Naming Binary Molecular Compounds

• Try the following:1. SO3

2. P4S10

3. NF3

4. N2O5. CH4

Writing Formulas for Binary Molecular Compounds

• Using the name, you can write the formula

• Write the formula for disulphur decafluoride. 1. Identify the first element, and give its symbol2. Identify the second element, and give its symbol:3. Add subscripts to indicate the numbers of atoms.4. Write the formula

Writing Formulas for Binary Molecular Compounds

• Try the following:1. sulphur hexabromide2. carbon tertachloride3. dinitrogen tetroxide4. tetraphosphorous decaoxide5. carbon dioxide

Homework

Complete the worksheet