Answer
\begin{matrix}
Symbol & Ion & Electrons & Protons \\
Te & Te^{2-} & 54 & 52\\
In & In^{3+} & 46 & 49 \\
Sr & Sr^{2+} & 36 & 38 \\
Mg & Mg^{2+} & 10 & 12 \\
Cl & Cl^- & 18 & 17
\end{matrix}
Work Step by Step
Ion commonly formed: Figure 4.14. page 110
Number of protons: Any periodic table, like figure 4.13, page 106.
Number of electrons = Number of protons - (ion charge)