Answer
\begin{matrix}
Symbol & Ion \space Formed & Electrons & Protons \\
Cl & Cl^- & 18 & 17 \\
Te & Te^{2-} & 54 & 52 \\
Br & Br^- & 36 & 35 \\
Sr & Sr^{2+} & 36 & 38
\end{matrix}
Work Step by Step
First column: Remove the charge from the ion to get the symbol of the element.
$Sr^{2+}(ion) \longrightarrow Sr \space(element \space symbol)$
Second column: See Figure 2.14 (Page 65) to identify the ion formed from the elements in the first column.
$Cl \longrightarrow Cl^-$
$Te \longrightarrow Te^{2-}$
Fourth column: See Figure 2.13 or any periodic table, and write the number above the respective symbol (atomic number).
$Te \longrightarrow 52$
$Br \longrightarrow 35$
Third column: Use the following equation to calculate the number of electrons in each ion:
$$n(e^-) = n(P) - charge$$
$n(e^-) = $number of electrons
$n(P) =$ number of protons
$Cl \longrightarrow n(e^-) = 17 - (-1) = 18$
$Br \longrightarrow n(e^-) = 35 - (-1) = 36$
$Sr \longrightarrow n(e^-) = 38 - (+2) = 36$
