Here's what I got.
You are not wrong, the questions does indeed require you to use ionization energies.
As you know, ionization energy describes the energy needed to remove one mole of electrons from one mole of atoms in the gaseous state.
#"X " + color(blue)(" energy") color(white)(x) -> " X"^(+) + " e"^(-)#
That represents the equation for the first ionization energy of a generic element
The total energy needed to form an
More specifically, you will have
#"Al" + color(blue)(E_1) -> "Al"^(+) + "e"^(-)#
#"Al"^(+) + color(blue)(E_2) -> "Al"^(2+) + "e"^(-)#
The first two ionization energies for aluminium are
This means that the total energy needed to form the
#E_"total" = color(blue)(E_1) + color(blue)(E_2)#
#E_"total" = 577.6 + 1816.6 = "2394 kJ/mol"#
Now all you need to do is check the ionization energies for the transition metals given to you. Since the transition metal ion carries a
As it turns out, cobalt is indeed the answer, since it requires a total ionization energy of
#E_"total" = 760 + 1648 = "2408 kJ/mol"#
to form the
SIDE NOTE I suspect that the data given to you in the booklet will point to an exact match between the two energy values.