Question

What is the formula for sodium nitride?

Answer 1

`"Na"_3"N"`

Explanation:

Sodium is an element in group 1 of the periodic table. As such, it will form an electron by losing a single electron to form a `"1+"` ion: `"Na"^+`.

Nitrogen is an element in group 5 of the periodic table. When it forms the nitride ion, it gains three electrons to form a `"3-"` ion: `"N"^(3-)`.

In ionic compounds, the charges of constituent ions must balance. This can be achieved by having three sodium ions per nitride ion. Therefore, the formula of sodium nitride is `"Na"_3"N"`.

However, `"Na"_3"N"` is extremely unstable. It rapidly decomposes into its constituent elements according to the equation:

`2"Na"_3"N" -> 6"Na" + "N"_2`

It lacks a boiling point because of this. Since ionic compounds have very high melting and boiling points as a result of the strong electrostatic attraction between oppositely charged ions that holds them together, sodium nitride should be no different; however, it will decompose as shown at around `360` Kelvin (`"K"`) or `86.85` `""^@ "C"`.