# What are the symbol formulae of barium oxide, rubidium nitride, and magnesium chloride?

Sep 24, 2016

Consider the position of each metal ion on the Periodic Table. An ionic compound requires that the charge of each ion sums to neutral.

#### Explanation:

And then consider the position of the gegenion, to get the charge of the non-metal.

$A .$ $\text{Barium and oxygen}$; barium is in Group 2, and tends to form $B {a}^{2 +}$ ions. Oxygen is in Group 16, and tends to form ${O}^{2 -}$ ions as its oxide. $B a O$ is the likely formula.

$B .$ $\text{Rubidium and nitrogen}$; barium is in Group 1, and exclusively forms $R {b}^{+}$ ions. Nitrogen is in Group 15, and tends to form ${N}^{3 -}$ ions as its nitride. $R {b}_{3} N$ is the likely formula.

$C .$ $\text{Magnesium and chlorine}$; magnesium is in Group 2, and tends to form......... Chlorine is in Group 17.............You tell me the formula?