Using only a periodic table, rank the elements in each set in order of increasing ionization energy

Question

Using only a periodic table, rank the elements in each set in order of increasing ionization energy .explain your ranking. a)B,N,F

b)F,C1,Br

c)Na,Cs,K

Answer 1

Ionization Energy (IE): the energy required to remove a valence electron from an atom of a particular element and create a positive cation (Losing a (-) electron causes the atom to develop a more positive overall charge). IE is directly proportional to the effective nuclear charge (z_eff), which is the degree of electrical force an electron "feels" from the nucleus. Z_eff increases as the # of protons increases (from left to right on the periodic table) and decreases as the # of electron energy levels increases due to the effect of electron "shielding". Overall: within a period/row, IE increases from left to right; and within a group/column, IE generally increases as you move UP the table. So...

a) B < N < F {all in period 2; in order of increasing atomic number}

b) Br < Cl < F {all in group VII; in order of decreasing # of energy levels and/or atomic radius}

c) Cs < K < Na {all in group I; same reasoning as in (b)}