A certain particle carries 2.5 × 10^–16 C of static electric charge. The number of electrons present in it would be:

The maximum number of neutrons are present in the nuclei of:
1. \(_8^{16}\mathrm{O}\)
2. \(_{12}^{24}\mathrm{Mg}\)
3.\(_{26}^{56}\mathrm{Fe}\)
4. \(_{38}^{88}\mathrm{Sr}\)

The number of protons, neutrons and electrons in  \( _{71}^{175}Lu\) respectively, are:

1. 104, 71 and 71

2. 71, 71 and 104

3. 175, 104 and 71

4. 71, 104 and 71

Which among the following are isoelectronic species?

1. ${\mathrm{Na}}^{+},<mspace\; width="1em"></mspace>{\mathrm{K}}^{+},<mspace\; width="1em"></mspace>{\mathrm{Ca}}^{2+},<mspace\; width="1em"></mspace>{\mathrm{Mg}}^{2+}$

2. ${\mathrm{Ca}}^{2+},<mspace\; width="1em"></mspace>{\mathrm{Mg}}^{2+},<mspace\; width="1em"></mspace>{\mathrm{S}}^{2-},<mspace\; width="1em"></mspace>{\mathrm{K}}^{+}$

3. ${\mathrm{Ca}}^{2+},<mspace\; width="1em"></mspace>\mathrm{Ar},<mspace\; width="1em"></mspace>{\mathrm{S}}^{2-},<mspace\; width="1em"></mspace>{\mathrm{K}}^{+}$

4. None of the above