Tertiary and Quaternary Compounds

Tertiary and Quaternary Compounds are compounds containing more than two elements. In naming them, the following procedures are followed:

(i) The name of the most electropositive element is written first followed by the most electronegative element.

(ii) If the metal has a variable oxidation number, its oxidation number is written in Roman numerals immediately after the element.

(iii) The oxidation number of the central atom is written in Roman numeral at the end of the radical. Example: Fe₂(CO₃)₃ – Iron (III) trioxocarbonate (IV).

(iv) Acid Radicals are named as hydrogen derivatives with the oxidation number of the central atom indicated at the end of the radical before writing the word “acid”.

Example: 

H₂SO₄ – Tetraoxosulphate (VI) acid

HNO₃ – Trioxonitrate (V) acid

(v) In metallic or ammonium hydroxide, the metallic radical or ammonium is named first, followed by the word hydroxide.

Example: 

NaOH – Sodium hydroxide, 

Ca(OH)₂ – Calcium hydroxide, 

NH₄OH – Ammonium hydroxide.