$\,\,{}^{13}_{6}\mathrm{C}$ : We know that, e = p = Z where, e = number of electrons, p = number of protons, Z = atomic number Here, e = 6 and A = 13 [Since A = Mass number] p = 6 n = A – p = 13 – 6 ⇒ n = 7 [Since A = p + n] Number of protons = 6 and number of neutrons = 7. $\,\,{}^{16}_{8}\mathrm{O}$ : Here, e = 8, p = 8, A = 16 n = A – p = 16 – 8 ⇒ n = 8 Number of neutrons = 8 and number of protons = 8. $\,\,{}^{24}_{12}\mathrm{Mg}$ : Here, e = 12, A = 24, p = 12 n = A – p = 24 – 12 ⇒ n = 12 Number of neutrons = 12 and number of protons = 12. $\,\,{}^{56}_{26}\mathrm{Fe}$ : Here, e = 26, p = 26, A = 56 n = A – p = 56 – 26 = 30 Number of neutrons = 30 and number of protons = 26. $\,\,{}^{88}_{38}\mathrm{Sr}$ : Here, e = 38, A = 88, p = 38 n = A – p = 88 – 38 ⇒ n = 50 Number of neutrons = 50 and number of protons = 38.