Chapter 4, Problem 5STP

Interpretation Introduction

Interpretation:For the given compounds, incorrect nomenclature has to be identified.

Concept introduction: If the group of atoms combines to form an ion, it is known as polyatomic ion.

General rules set for the nomenclature of binary ionic compounds are as follows:

• Position ofboth cation and anion forming element in the periodic table has to be identified for an idea of their oxidation states.
• Always the cationic species name is retained and placed first in nomenclature.
• After the cation name, anion name is placed with suffix ‘-ide’ at the end of its root name.
• The oxidation state is expressed as Roman numeral after cation name, enclosed in bracket. Such as copper(II) oxide.

Answer to Problem 5STP

B is incorrect nomenclature.

Explanation of Solution

For nomenclature of polyatomic anion, prior knowledge of composition of atoms in ion and its charge is must. Generally, polyatomic anion name ends with −ate with a few exceptions.

For sulfates $({\text{SO}}_4{}^{2-})$ ,nitrates $({\text{NO}}_3{}^{-})$ and carbonates $({\text{CO}}_3{}^{2-})$ this rule is followed.

But in case of $({\text{SO}}_3{}^{2-})$ the name becomes sulfite not sulfate $({\text{SO}}_4{}^{2-})$ . Similar is case of $({\text{NO}}_2{}^{-})$ where the naming done as nitrite not nitrate $({\text{NO}}_3{}^{-})$ .

So, option (B) is an incorrect nomenclature.

Conclusion

  ${\text{NH}}_4^{+}$ is correctly named as ammonium ion as the root name is ammonia with suffix ‘ium’.

  ${\text{CO}}_3^{2-}$ is correctly named as carbonate ion as the root name is carbon plus suffix ‘ate’.

Nitriteis the correct nomenclature for polyatomic ion ${\text{NO}}_2^{-}$ .