Chapter U1.21, Problem 6E

Interpretation Introduction

Interpretation: Examples of three ionic compounds with metal to non-metal ratio of 1:2 are to be given and the total number of valence electrons in each compound has to be specified. Also, the compound names have to be given.

Concept Introduction: Ionic compounds are formed between metals and nonmetals. The metals and nonmetals in the periodic table can combine in a variety of ways to form a large number of ionic compounds. Valence electrons are electrons in the outermost orbit of an atom.

Answer to Problem 6E

The following table shows ionic compounds formed with metals to nonmetals ratio of 1:2.

Metal	Nonmetal	Compound	Number of valence electrons
Mg	Cl	MgCl2-sodium chloride	16
Ba	I	BaI2- barium iodide	16
Ca	Br	CaBr2- calcium bromide	16

Explanation of Solution

Given information:

Metal to nonmetal ratio in ionic compounds is 1:2.

For a compound to have metal to nonmetal ratio of 1:2, the metal must have two valence electrons and the nonmetal must have seven valence electrons. For every metal atom, two nonmetal atoms are needed to fulfill a noble gas configuration. Sothe total number of valence electrons in the compound is 16. So the metal must be from group 2A and nonmetal must be from group 7A. Metals of group 1A or group 2 are beryllium, calcium, magnesium, strontium, barium and radium. Nonmetals of group 7 A are halogens like fluorine, chlorine, bromine, iodine and astatine. The charges on metals are +2 and nonmetals are -1 which together add up to zero.

To name the compound, the metal name comes first and then the nonmetal name is changed to “-ide”.

The ionic compounds possible are therefore magnesium chloride, magnesium bromide, magnesium iodide, magnesium fluoride, calcium chloride, calcium bromide, barium bromide, barium chloride, etc.

Conclusion

Metals and nonmetals combine to form ionic compounds. Such compounds are called salts.