Which among the following is an example of an odd electron molecule?

The lattice energy of $NaCl$ is $-780 \, kJ \, mol^{-1}$. The enthalpies of hydration of $Na^{+}_{(g)}$ and $Cl^{-}_{(g)}$ ions are $-406 \, kJ \, mol^{-1}$ and $-364 \, kJ \, mol^{-1}$ respectively. The enthalpy of solution of $NaCl_{(s)}$ is $..... \, kJ \, mol^{-1}$.

Which of the following species exists?

Choose the correct order for the given properties.

Sodium bicarbonate $(NaHCO_3)$ has:

What is the total number of planes in $CH_4$ that contain the maximum number of atoms?