The maximum number of neutrons are present in the nuclei of

$1.$ ${\mathrm{O}}_8^{16}$
$2.$ ${\mathrm{Mg}}_{12}^{24}$
$3.$ ${\mathrm{Fe}}_{26}^{56}$
$4.$ ${\mathrm{Sr}}_{38}^{88}$

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

The electron of a Br atom that experiences the lowest effective nuclear charge is:

1. 2p and 3p

2. 4p

3. 2p

4. 3p

Which among the following are isoelectronic species?

1. ${\mathrm{Na}}^{+}, {\mathrm{K}}^{+}, {\mathrm{Ca}}^{2+}, {\mathrm{Mg}}^{2+}$

2. ${\mathrm{Ca}}^{2+}, {\mathrm{Mg}}^{2+}, {\mathrm{S}}^{2-}, {\mathrm{K}}^{+}$

3. ${\mathrm{Ca}}^{2+}, \mathrm{Ar}, {\mathrm{S}}^{2-}, {\mathrm{K}}^{+}$

4. None of the above