What is the formula for sodium nitride?

1 Answer
Owen Bell
Jan 5, 2016

#"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"#.

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