Chapter 4

Question 1

Ionisation energy?

Answer 1

Ionization energy (IE) is the minimum energy required to remove an electron from
an atom in the gas phase.

Question 2

Electron affinity?

Answer 2

Electron affinity (EA) is the energy released when an atom in the gas phase
accepts an electron.

Question 3

Nuclear charge and shielding?

Answer 3

Nuclear charge (Z) is simply the number of protons in the nucleus of an atom. 
Effective nuclear charge (Zeff) is the actual magnitude of positive charge that is “expe-
rienced” by an electron in the atom. The only atom in which the nuclear charge and 
effective nuclear charge are the same is hydrogen, which has only one electron. In all 
other atoms, the electrons are simultaneously attracted to the nucleus and repelled by one 
another. This results in a phenomenon known as shielding.