Compounds: Introduction to Nomenclature & Formulas

Science 10: Chemical Reactions

Outcomes

Name and write formulae for common ionic compounds and molecular compounds and describe the usefulness of the IUPAC nomenclature system (319-1, 114-8)

Atomic Theory

All matter is composed of incredibly tiny particles called atoms.

Atoms cannot be created, destroyed, or divided into smaller particles by a physical or chemical change.

Atoms of difference elements bond in definite proportions to form compounds.

Review of Terms

Element – a pure substance that can not be broken down further by physical or chemical means

Atom – the smallest unit of an element that has the properties of that element

Sub-Atomic Particles

Proton – positive charge Neutron – neutral charge Electron – negative charge In any neutral atom the number of

electrons equals the number of protons.

The atomic number of an element is the number of protons that an atom of that element has.

Anatomy of an Atom

Elements Uniting

Compounds are composed of more than one type of element bonded together.

Ex. NaCl H2O HCl NaOH CO2

There are 2 main types of compounds:

ionic & molecular

Molecular Compounds

A compound formed of atoms of two or more elements that share electrons.

The smallest independent unit of a molecular compound is a molecule, which are particles of atoms joined together by covalent bonds.

Ionic Compounds

A compound composed of oppositely charged ions held together with ionic bonds.

An ion is an atom or group of atoms with a positive or negative charge.

Electrons and Lewis Dot Diagrams

Binary Ionic Compounds

Are composed of ions of two different elements: a positively charged metal ion and a negatively charged non-metal ion

Rules for Naming

1. Name the positive ion first by writing the full name of the metallic element.

2. Name the non-metal ion next by dropping the last syllable(s) of the name of the element and adding the suffix "ide.“

Example: Magnesium and Oxygen Magnesium Oxide

Example

What would we name a compound of Li and S?

Rules for Writing Formulas

1. Using the name of the binary compound, write the symbols and charge for the ions involved. Write the ion charge as a superscript. Example: aluminum Oxide — Al3+ O2-

2. Put the charges of each ion as the subscript of its partner "cross the charge." Example:

Al23+ O32-

3. As a check to ensure the formula is written correctly, multiply the charge for each ion by the subscript for the same ion. The total positive charge should equal the total negative charge and the net charge per ionic formula should be zero. Example:

A13+ x 2 = 6+ O2- x 3 = 6- 6 + 6- = 0 4. Write the final chemical formula without the charges. Final Answer: Al2O3

Example

What is the formula for magnesium chloride?