Examine the following set of ionization energy values for a certain element. How many valence electrons does an atom of the neutral element possess?

Ionization step Ionization Energy (kJ/mol)

Ei1 1012

Ei2 1903

Ei3 2912

Ei4 4956

Ei5 6273

Ei6 22233

Ei7 25997

Enter the answer numerically as an integer.

5

Explanation:

Let us look at the values very closely. It is easy to see that the first to the fifth ionization energies of the element are closely related to each other. Recall that the ionization energy increases as the the number of electrons removed from the outermost shell of the atom increases. Hence E1
However, the sixth and seventh ionization energies shows a jump, the ionization energy suddenly increases by a very high magnitude. This can not suggest the removal of a valence shell electron but the removal of inner or core electrons. Hence the answer.