Nomenclature – binary compounds of metals with fixed charge (I)

Introduction

By now you know that chemistry has its own "language" — a set of naming rules created by IUPAC so that scientists anywhere in the world can understand exactly which substance is being talked about (Talbot, p.172). Today we start with one of the simplest but most important parts of this language: naming binary compounds — compounds made of just two elements — where the metal involved always forms one fixed ionic charge.

What is a binary compound?

A binary compound contains only two different elements. When one of these elements is a metal and the other is a non-metal, the compound is usually ionic: the metal loses electrons to form a positive ion (cation), and the non-metal gains electrons to form a negative ion (anion).

Metals with a fixed charge

Some metals always form the same charge in their compounds. These are mainly:

• Group 1 metals → always form a 1+ ion (Li⁺, Na⁺, K⁺...)
• Group 2 metals → always form a 2+ ion (Mg²⁺, Ca²⁺, Ba²⁺...)
• Aluminium (group 13) → always forms a 3+ ion (Al³⁺)
• Silver (Ag⁺) and Zinc (Zn²⁺) are common transition metal exceptions that also have only one possible charge.

Because these metals only ever form one type of ion, we do not need to state their charge in the compound's name (Talbot, p.130). This is different from transition metals like iron or cobalt, which can form more than one charge and need extra notation (you'll meet this in the next lesson!).

The naming pattern

For a binary ionic compound of a fixed-charge metal with a non-metal:

name of metal + (stem of non-metal) + "-ide"

The non-metal's name is shortened to its stem and given the ending -ide.