Question

Which elements does not combine directly with nitrogen at high temperature?

• A. Li
• B. Rb
• C. Sr
• D. Mg

Answer 1

The correct option is B Rb

Only $Rb$ does not combine with $N_2$ at high temperature. Because heavier metals like $Rb$ are seen to be chemically inactive towards $N_2$ upon heating.

Since the nitride ion holds a high formal charge $\left(N^{3-}\right)$ and contains an adverse molar ration of cations to anions $(3:1)$

it is impossible to form a stable structure. But alkali metal $Li$ can react with $N_2$ at room temperature. $Sr$ and $Mg$ can react with $N_2$ at high temperature.

So, the correct option is $Rb$