Tetrasodium pyrophosphate (diphosphate) has the anion $\mathrm{P}{}_2\mathrm{O}{}_7{}^{4-}$ (O is $-2$). Which option correctly gives its formula, the oxidation number of P, and the total number of atoms in one formula unit?

1. A$\mathrm{Na}{}_4\mathrm{P}{}_2\mathrm{O}{}_7$, $+4$, 13 atoms
2. B$\mathrm{Na}{}_4\mathrm{P}{}_2\mathrm{O}{}_7$, $+5$, 7 atoms
3. C$\mathrm{Na}{}_4\mathrm{P}{}_2\mathrm{O}{}_7$, $+5$, 13 atoms
4. D$\mathrm{Na}{}_2\mathrm{P}{}_2\mathrm{O}{}_7$, $+5$, 11 atoms