Chapter 4, Problem 11STP

(a)

Interpretation Introduction

Interpretation:

The reason behind need of roman numerals in naming binary compounds is to be discussed with example.

Concept introduction:

Roman numerals are used when binary compound contains type-II metals.

Answer to Problem 11STP

Roman numerals indicate the charge carried by metal. It is necessary to mention the charge when metal can form more than one cation. For example, copper can form $C{u}^{+}andC{u}^{2+}$ . So to identify the actual ion in binary compound, roman numeral is used.

Explanation of Solution

$C{u}_{2}O$ is a binary compound of non-metal with non-metal. Oxide ion carries -2 charge so to balance charge copper should be carrying +1 charge. Therefore, its name is Copper (I) oxide.

$CuO$ is a binary compound of non-metal with non-metal. Oxide ion carries -2 charge. So to balance charge copper should be carrying +2 charge. Therefore, its name is Copper (II) oxide.

(b)

Interpretation Introduction

Interpretation:

The reason behind need of prefixes in naming binary compounds is to be discussed with example.

Concept introduction:

Prefixes like mono, di, tri, tetra are used to indicate number of anions present in the binary compound.

Answer to Problem 11STP

Prefixes are used when a non-metal is joined with non-metal. As the bonding is covalent to show number of one non-metal attached with other, prefixes are used.

Explanation of Solution

Boron trifluoride is a binary compound of non-metal with non-metal. So, its formula is $B{F}_3$

A binary compound $S{F}_6$ is named as sulphur hexafluoride to indicate six fluorine atoms.