Question

Ionization enthalpy of Li is 520 kJ mol^-1 while that of F is 1681 kJ mol^-1. Explain.

Answer 1

• Both Li and F belong to period 2. 
• Across a period, the screening effect is the same while the effective nuclear charge increases. 
• As a result, the outer electron is held more tightly and therefore, the ionization enthalpy increases across a period. 
• Hence, F will have higher ionization enthalpy than Li.

Thus,

Ionization enthalpy of Li is 520 kJ mol^-1 while that of F is 1681 kJ mol^-1.