91Ó°ÊÓ

It is given that the ion has a \(3 + \) charge, \(28\)electrons, and a mass number of \(71\).

The atomic numberof an atom \( = \) Number electrons \( + \)atomic charge

\(\begin{aligned}{}& = 28 + 3\\ &= 31\\ &= Ga\left( {{\rm{gallium}}} \right)\end{aligned}\)

Therefore, the symbol of the ion: \({}_{31}^{71}G{a^{3 + }}\)

It is given that the ion has\(36\)electrons,\(35\)protons, and\(45\)neutrons.

The atom with number of protons\( = \)atomic number

\(\begin{aligned}{}& = 35\\ &= Br{\rm{(Bromine)}}\end{aligned}\)

Mass number ofbromine\((Br) = \)Number of neutrons\( + \)Number of protons

\(\begin{aligned}{}& = 35 + 45\\ &= 80\end{aligned}\)

The charge on bromine\((Br) = \)Number of protons \( - \)Number of electrons

\(\begin{aligned}{}& = 35 - 36\\ &= - 1\end{aligned}\)

Therefore, the symbol of the ion: \({}_{35}^{80}B{r^{ - 1}}\)

It is given that the ion has\(86\)electrons,\(142\)neutrons, and a\(4 + \)charge.

The atomic number\( = \)Electrons\( + \)Charge on atom

\(\begin{aligned}{}& = 86 + 4\\ &= 90\\ &= Th{\rm{(Thorium)}}\end{aligned}\)

Mass number ofThorium\((Th) = \)Number of neutrons\( + \)Number of protons

\(\begin{aligned}{}& = 90 + 142\\ &= 232\end{aligned}\)

Therefore, the symbol of the ion: \({}_{90}^{232}T{h^{4 + }}\)

It is given that the ion has a \(2 + \) charge, atomic number \(38\), and mass number \(87\).

The atom with the atomic number \(38\) and mass number \(87\) is strontium\(\left( {Sr} \right)\).

Therefore, the symbol of the ion: \({}_{38}^{87}S{r^{2 + }}\)