Which of the following elements has a greater effective nuclear charge?

Question

Which of the following elements has a greater effective nuclear charge?

a	Radium (Ra)
b	Bismuth (Bi)
c	Francium (Fr)
d	Iodine (I)

Answer 1

The effective nuclear charge on an electron is given by the following equation:

Z_eff = Z – S

where Z is the number of protons in the nucleus (atomic number), and S is the number of non valence electrons).

Ra = 88- 86 = 2

Bi = 83 - 78 = 5

Fr = 87- 86 =1

I = 53- 46 = 7

The answer is Iodine

Answer 2

The effective charge is the effective charge that the valence electrons experience from the nucleus of the atom. The effective charge equation is Z(eff)=(number of protons in nucleus)-(number of non-valence electrons or shielding electrons)

If we take each one then:

Ra has 88 protons and 86 non-valence electrons therefore Z(eff)=88-86=2

Bi has 83 protons and 78 non-valence electrons therefore Z(eff)=83-78=5

Fr has 87 protons and 86 non-valence electrons therefore Z(eff)=87-86=1

I has 53 protons and 46 non-valence electrons therefore Z(eff)=53-46=7

Therefore we can say that Iodine has the largest effective nuclear charge at 7.