Naming Salts

Introduction

Chemists name salts using a simple system that tells you exactly where each part came from. Once you know which acid gives which ending, you can name hundreds of salts without memorising them one by one. "Magnesium sulfate" means a salt of magnesium and sulfuric acid; "calcium ethanoate" means a salt of calcium and ethanoic acid. This page sets out the rules and the common families: chlorides, sulfates, nitrates, carbonates and ethanoates.

Core explanation

Two words, two parents. A salt name has two parts. The first word is the metal (or ammonium), with its name unchanged. The second word comes from the acid . For example, sodium + hydrochloric acid gives sodium chloride.

The acid families.

Acid Formula Salt ending Anion --- --- --- --- Hydrochloric acid HCl chloride Cl⁻ Sulfuric acid H₂SO₄ sulfate SO₄²⁻ Nitric acid HNO₃ nitrate NO₃⁻ Carbonic acid H₂CO₃ carbonate CO₃²⁻ Ethanoic acid CH₃COOH ethanoate CH₃COO⁻ Phosphoric acid H₃PO₄ phosphate PO₄³⁻

-ide and -ate. The ending -ide usually means the anion is a single element, such as chloride (Cl⁻), bromide (Br⁻) or oxide (O²⁻). The ending -ate means the anion contains oxygen as well, such as sulfate (SO₄²⁻), nitrate (NO₃⁻) and carbonate (CO₃²⁻). Hydroxide (OH⁻) is an exception worth remembering: it ends in -ide but contains oxygen and hydrogen.

Carbonates. Carbonic acid is too unstable to keep in a bottle, but its salts, the carbonates, are very common, such as calcium carbonate in limestone and sodium carbonate in washing soda.

Ethanoates. Ethanoic acid, the acid in vinegar, is a weak organic acid. Only the hydrogen in the –COOH group is replaced, giving salts such as sodium ethanoate, CH₃COONa. Older books call these acetates.

Metals with more than one ion. Transition metals such as iron and copper can form ions with different charges. A Roman numeral in brackets shows which: iron(II) sulfate contains Fe²⁺, while iron(III) chloride contains Fe³⁺. Copper(II) sulfate contains Cu²⁺. Metals with only one common ion, such as sodium, magnesium or zinc, do not need a numeral.

Ammonium salts. When ammonia is the base, the first word is "ammonium": ammonium chloride, ammonium sulfate, ammonium nitrate.

Hydrogen salts. If only some of an acid's hydrogen is replaced, the word "hydrogen" appears before the anion: sodium hydrogencarbonate (NaHCO₃), sodium hydrogensulfate (NaHSO₄).

Step-by-step reasoning

To name a salt from a reaction:

1. Identify the metal, or ammonium if the base is ammonia. 2. Add a Roman numeral if the metal can form more than one ion. 3. Identify the acid and choose the matching ending. 4. Combine: metal name first, then anion name.

Visual explanation

Draw a two-column "menu": metals on the left (sodium, potassium, calcium, magnesium, zinc, copper(II), iron(III), ammonium) and anions on the right (chloride, sulfate, nitrate, carbonate, ethanoate). Any item from the left joined to any item on the right gives a salt name.

Real-world analogy

Salt names work like double-barrelled surnames that record both parents. "Potassium nitrate" tells you the metal "parent" is potassium and the acid "parent" is nitric acid, just as a family name can record both sides of a family.

Real-world example

Food labels use salt names: sodium chloride (table salt), calcium carbonate (a calcium supplement and firming agent), sodium hydrogencarbonate (baking soda) and potassium sorbate. Some preservatives are ethanoates, such as sodium ethanoate, used to control acidity.

Why?

Why do sulfuric acid salts end in -ate and hydrochloric acid salts in -ide? The sulfate ion contains oxygen as well as sulfur, while the chloride ion is a single chlorine atom. The endings encode the composition of the anion.

Common misconception

"Sulfide and sulfate are the same." Sulfide is S²⁻, a single sulfur ion, from hydrogen sulfide. Sulfate is SO₄²⁻, containing four oxygen atoms, from sulfuric acid. They form quite different salts.

Worked example

Question: Name the salt formed when iron(III) oxide reacts with hydrochloric acid, and when calcium carbonate reacts with ethanoic acid.

Reasoning: Iron keeps its +3 charge, so the salt is iron(III) plus chloride. Calcium with ethanoic acid gives calcium plus ethanoate.

Answer: Iron(III) chloride; calcium ethanoate.

Quick check

1. Name the salt formed from potassium hydroxide and nitric acid. Answer: Potassium nitrate.

Exam focus

Learn the acid–ending pairs, especially hydrochloric → chloride, sulfuric → sulfate and nitric → nitrate. Remember Roman numerals for transition metals and "ammonium" for ammonia. Questions often give a reaction and ask for the name of the salt.

Advanced insight

The -ite ending indicates an oxoanion with fewer oxygen atoms than the -ate form, such as sulfite (SO₃²⁻) versus sulfate (SO₄²⁻) and nitrite (NO₂⁻) versus nitrate (NO₃⁻). Sodium nitrite, for example, is used in curing meats. Systematic naming keeps these closely related ions clearly distinct.

Summary

A salt name has the metal (or ammonium) first and an anion name from the acid second: hydrochloric acid gives chlorides, sulfuric acid sulfates, nitric acid nitrates, carbonic acid carbonates and ethanoic acid ethanoates. -ide means a single-element anion; -ate means it contains oxygen. Roman numerals show the charge on metals such as iron and copper.

Practice questions

1. Name the salt formed when zinc reacts with sulfuric acid. Answer: Zinc sulfate. 2. Which acid produces nitrate salts, and which produces ethanoate salts? Answer: Nitric acid produces nitrates; ethanoic acid produces ethanoates. 3. Explain what the (II) in copper(II) chloride means. Answer: It shows the copper ion has a 2+ charge, Cu²⁺. 4. Name the salt formed from ammonia and hydrochloric acid. Answer: Ammonium chloride. 5. What does the ending -ate tell you about an anion? Answer: It contains oxygen combined with another element, as in sulfate or nitrate.