The action of concentrated $H_{2}S{O}_4$ on urea $N{H}_{2}CON{H}_2$, results in the production of a white crystalline solid X. This is a monobasic acid which on treating with nitrite ion and dil HCl liberates one mole of $N_2$, and on addition of ${\text{aq BaCl}}_{\text{2}}$. The resulting solution yields one mole of BaSO₄ per mole of X. The total number of atoms in X is