the stable binary compound.a) MgNa b) Mg:Ns c) MgN d) MgN2

The stable binary compound among the given options is MgN2.

Here's why:

a) MgNa: This is not a valid compound. Magnesium (Mg) is a +2 cation and Sodium (Na) is a +1 cation. Two cations cannot combine to form a stable compound.

b) Mg:Ns: This is not a valid compound. There is no element symbolized by 'Ns'.

c) MgN: This is not a valid compound. Magnesium (Mg) is a +2 cation and Nitrogen (N) is a -3 anion. The charges do not balance out to form a stable compound.

d) MgN2: This is a valid compound. Magnesium Nitride (Mg3N2) is a stable compound. Magnesium (Mg) is a +2 cation and Nitrogen (N) is a -3 anion. When they combine in a ratio of 3:2, the charges balance out to form a stable compound.