Chapter 4

Q. 4.4

Show the formation of the following ionic compounds using Lewis structures.
a. Na_{3}N        b. MgO        c. Al_{2}S_{3}


Verified Solution

a. Sodium (a Group IA element) has one valence electron, which it would “like” to lose. Nitrogen (a Group VA element) has five valence electrons and would thus “like” to acquire three more. Three sodium atoms are needed to supply enough electrons for one nitrogen atom.

b. Magnesium (a Group IIA element) has two valence electrons, and oxygen (a Group VIA element) has six valence electrons. The transfer of the two magnesium valence electrons to an oxygen atom results in each atom having a noble-gas electron configuration. Thus these two elements combine in a one-to-one ratio.

c. Aluminum (a Group IIIA element) has three valence electrons, all of which need to be lost through electron transfer. Sulfur (a Group VIA element) has six valence electrons and thus needs to acquire two more. Three sulfur atoms are needed to accommodate the electrons given up by two aluminum atoms.