Chapter 4, Problem 31A

Interpretation Introduction

Interpretation:

The terms binary compound, polyatomic anion and oxyanion is to be explained.

Concept introduction:

Binary compound means compound containing two units.

Polyatomic ion involves more than one atom which carries a net charge and exists as a single unit. Oxyanion is an anion of oxygen and another non-metal. For example: sulphate ion $(S{O}_4{}^{2-})$ , Phosphate ion $(P{O}_4{}^{3-})$

Answer to Problem 31A

A binary compound is the compound having two components.

Binary compounds are of three types:

• Type-I: Compound in which a metal forms ionic bond with a non-metal and the metal can form only one type of ions.
• Type-II: Compound in which a metal forms ionic bond with a non-metal and the metal can form more than one type of ions.
• Type-III: Compound in which a non-metal forms bond with a non-metal.

Examples of binary compound:

Ammonium chloride, silver sulphide, copper (I) chloride.

Polyatomic ion contains more than one atom which carries a net charge and exists as a single unit. Example: ammonium ion, cyanide ion.

Oxyanion is a class of polytomic anion. In it, one atom is always oxygen. Example: sulphate, phophate

Explanation of Solution

To name binary compounds of various types, some rules are assigned:

Rules for naming these compounds:

Type-I:

1. Name of metal cation is written as name of element.
2. Name of anion is written using root name and adding ‘ide’ to it.
3. Writing these names in the same sequence gives the name of compound.

Type-II:

1. Name of metal cation is written as name of element followed by charge carried by it in roman numerals in bracket.
2. Name of anion is written using root name and adding ‘ide’ to it.
3. Writing these names in the same sequence gives the name of compound.

Type-III:

1. It is name by writing the name of first element as same as element.
2. Second element in anionic form and prefixes are used to denote the number of atoms. Prefix mono is not used for first element.

When metal is bonded with polyatomic ion, rules are similar to ionic binary compounds.

The rules which are used to name series of oxyanions are:

• The standard anion ends with ‘ate’.
• For the anion carrying one more oxygen, prefix ‘per’ is used.
• The anion carrying one less oxygen atom ends with ‘ite’.
• The anion carrying two less oxygen ends with ‘ite’ and prefix ‘hypo’ is also used.

Conclusion

Thus, combination of two components in a compound make it binary.