Chapter 4, Problem 4STP

Interpretation Introduction

Interpretation: The incorrect nomenclature for these compounds has to be identified.

Concept introduction: An ionic compound containing only two elements in the form of a cation and a anion, is called a binary ionic compound.

To name a compound, certain rules are followed. The given compounds are binary compounds.

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.

There is one another type of compound in which metal is bonded with a polyatomic ion

Answer to Problem 4STP

All compounds are correctly named.

Explanation of Solution

Rules for naming these compounds:

Type-I:

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

Type-II:

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

Type-III:

• It is name by writing the name of first element as same as element.
• 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.

All compounds are named as per the rules so are correct.

Conclusion

In cobalt(II) chloride, element $\text{Co}$ has $+2$ state so II is used in bracket and chlorine is suffixed with -ide attached to its root name hence it is correctly named.

Similarly, magnesium oxide, aluminum (III) oxide and diphosphorus pentoxide are also correct.