The question is asking for the correct order of the valencies of the elements Ne, Si, N, and Mg. Valency refers to the combining capacity of an element, or how many electrons it needs to gain or lose in order to achieve a stable electron configuration.

Option 1: Ne < Mg < N < Si

This option suggests that the valency of Ne is the lowest, followed by Mg, then N, and finally Si. This means that Ne requires the fewest number of electrons to achieve a stable configuration, while Si requires the most.

Option 2: Si < N < Mg < Ne

This option suggests the opposite order, with Si having the lowest valency, followed by N, Mg, and then Ne. This contradicts the provided correct answer.

Option 3: Ne < N < Si < Mg

This option matches the correct answer provided, with Ne having the lowest valency, followed by N, Si, and finally Mg. This means that Ne requires the fewest electrons, while Mg requires the most.

Option 4: Mg < Ne < N < Si

This option suggests that Mg has the lowest valency, followed by Ne, then N, and finally Si. This contradicts the provided correct answer.

In conclusion