Answer
Please see the work below.
Work Step by Step
We know that
$K^+$ has 19 protons 18 electrons.
$Mg^{+2}$ has 12 protons and 10 electrons.
$Fe^{+3}$ has 26 protons and 23 electrons.
$Br^-$ has 35 protons and 36 electrons.
$Mn^{+2}$ has 25 protons 23 electrons.
$C_4^-$ has 6 protons and 10 electrons.
$Cu_2^+$ has 29 protons and 27 electrons.
