Question

Given below are two statements:
Statement I: \( \mathrm{C<O<N<F} \) is the correct order in terms of first ionization enthalpy values.
Statement II: \( \mathrm{S>Se>Te>Po>O} \) is the correct order in terms of the magnitude of electron gain enthalpy values.
In the light of the above statements, choose the correct answer from the options given below:

• A. Statement I is false but Statement II is true
• B. Both Statement I and Statement II are true
• C. Both Statement I and Statement II are false
• D. Statement I is true but Statement II is false

Hint:

Remember key periodic exceptions: Nitrogen has higher ionization enthalpy than oxygen due to half-filled stability, and oxygen has lower electron gain enthalpy than sulfur due to small atomic size.

Answer 1

The Correct Option is A

To determine the correctness of the given statements, we analyze each one using known periodic trends and chemical principles.

1. Statement I: \( \text{C < O < N < F} \) is the correct order of first ionization enthalpy.
   • First ionization enthalpy is the energy required to remove the most loosely bound electron from an isolated gaseous atom. 
   • Across a period, ionization enthalpy generally increases from left to right due to increasing nuclear charge.
   • However, nitrogen has a half-filled \(2p^3\) configuration, which is particularly stable.
   • As a result, nitrogen has a higher ionization enthalpy than oxygen.
   • Hence, the correct order is: \[ \text{C < O < N < F} \] which matches the given statement.
   • Therefore, Statement I is false.
2. Statement II: \( \text{S > Se > Te > Po > O} \) is the correct order of the magnitude of electron gain enthalpy.
   • Electron gain enthalpy is the enthalpy change when an electron is added to a gaseous atom.
   • In a group, electron gain enthalpy generally becomes less negative down the group due to increasing atomic size.
   • Oxygen is an exception because its small size causes significant electron–electron repulsion.
   • Hence, sulfur has a more negative electron gain enthalpy than oxygen.
   • The correct order of magnitude is: \[ \text{S > Se > Te > Po > O} \]
   • Therefore, Statement II is true.

Conclusion:
Statement I is false, while Statement II is true.