C2 : 2.3-Naming Ionic Compounds

An important part of dealing with chemical compounds is knowing how to refer to them. Learn to name all ionic compounds, including simple binary compounds, compounds containing transition metals and compounds containing polyatomic ions.

An ionic compound is chemical compound in which ions a held together by ionic bond. Usually, the positive charged portion consists of metal cation and negatively charged portion is an anion or polyatomic ion

CATION :

All cations are derived from metal atoms ( Na⁺, Mg²⁺, Al³⁺ )except ammonium ion ; NH₄⁺ and hydronium ion, H₃O⁺

Many metals (particularly transition elements) can form more than one ion, each with particular charge ^. Example : Fe²⁺  :  iron(II),  Fe³⁺  :  iron(III) 

ANION

Name of anion takes the root of the nonmetal and add suffix “–ide”

Examples are oxide (O^2-), sulfide (S^2-), fluoride (F^-), chloride (Cl^-), bromide (Br^-), iodide (I^-), nitride (N^3-), hydride (H^-)

To name an ionic compound you simply need to find the names of the cation and anion present in the compound.

1. Identify the cation:
• The cation is always written first in the formula for an ionic compound.
2. Identify the anion:
• Cover up the cation. Everything that is leftover will be the anion.
3. Write the name of the ionic compound by writing the name of the cation followed by the name of the anion

Example 1: Write the correct name for the compound whose empirical formula is Na₂SO₄.

1. Na₂SO₄ is an ionic compound because it contains a metal (Na) and two non-metals (S and O).
2. Identify the cation:
• The cation will be the first element written: Na₂SO₄
  • sodium ion
3. Identify the anion:
• The anion will be everything leftover once the cation has been identified: Na₂SO₄
  • sulfate ion
4. The correct name for Na₂SO₄ is sodium sulfate. 

Example 2: Write the correct name for the compound whose empirical formula is (NH₄)₂CO₃.

1. Even though this compound is composed of only non-metals, it is still an ionic compound. (It starts with NH₄.)
2. Identify the cation:
• The cation will always be the first ion written.
  • This compound contains the only common polyatomic cation. (NH₄)₂CO₃
    • ammonium ion
3. Identify the anion:
• The anion will be everything leftover once the cation has been identified: (NH₄)₂CO₃
  • carbonate ion
4. The correct name for this compound is ammonium carbonate.

Example 3: Write the correct name for the compound whose empirical formula is SnO₂.

1. This compound is an ionic compound. It contains a metal (Sn) and a non-metal (O).
2. Identify the cation:
• The cation is always written first in the formula.
  • SnO₂
• Tin can form two different cations Sn²⁺ and Sn⁴⁺). You must correctly identify its charge.
  • The charges of the cation and the anions must exactly balance out.
  • Since there are two anions and each one has a 2- charge, there is a total negative charge of 4-. In order to balance out the negative charge, the single tin ion must have a 4+ charge.
    • tin (IV) ion
3. Identify the anion:
• The anion will be everything leftover once the cation has been identified.
• SnO₂
  • oxide ion
4. The correct name for the compound is tin (IV) oxide.

Further example :