(1) an atom with the electron configuration 1s22s22p2 possesses two valence electrons.
(2) the formula of the ionic compounds that contains ba2+ and n3- ions is ba2n3.
(3) the polyatomic ions nitrate and azide are both tetraatomic entities.

a) all three statements are true.
b) two of the three statements are true.
c) only one of the statements is true.
d) none of the statements is true.

d) None of the statements is true.

Explanation:

(1) FALSE.

The valence electrons are the electrons from the valence shell. For the electron configuration given, the valence shell is 2s²2p², so there are 2 electrons in subshell 2s, and 2 electrons in subshell 2p, then there are 4 valence electrons.

(2) FALSE.

To form an ionic compound, first we put the cation and then the anion, and the charge of one is the amount of the other, so for Ba²⁺ and N³⁻, the compound is Ba₃N₂.

(3) FALSE.

The ion nitrate is NO₃⁻, and it has 4 atoms (1 N and 3 O) so it is tetratomic. The ion azide is N₃⁻, and it has 3 atoms, so it is triatomic.