Question

Which of the following has lowest ionisation energy?

• A. Oxygen
• B. Nitrogen
• C. Fluorine
• D. Sulphur

Answer 1

Answer: (D)

Sulphur

Answer 2

Among oxygen, nitrogen, fluorine and sulphur, the lowest ionisation energy is of sulphur. As their first ionisation values indicated below $N=1402.1 KJ/mol, O=1313.7 \, kJ/mol$, $F=1680.8 \, kj/mol, S=999.4 \,k/J mol$ As down the group, the number o f inner shells increases. Therefore ionisation energy decreases due to screening effect.