Question
Question: The first ionisation enthalpy of Na, Mg and Si are 496, 737, 776 kJ/mol respectively. What will be t...
The first ionisation enthalpy of Na, Mg and Si are 496, 737, 776 kJ/mol respectively. What will be the first ionisation enthalpy potential of Al in kJ/mol?
A
496
B
737
C
776
D
577
Answer
577 kJ/mol
Explanation
Solution
Ionization enthalpy generally increases across a period. However, Al has a lower first ionization enthalpy than Mg due to Mg's stable, filled 3s² electron configuration, making its 3p¹ electron easier to remove. Thus, the trend is IE(Na) < IE(Al) < IE(Mg) < IE(Si). Given IE(Na)=496, IE(Mg)=737, and IE(Si)=776 kJ/mol, IE(Al) lies between 496 and 737 kJ/mol. The accepted value for Al is approximately 577 kJ/mol.