Question

The second electron gain enthalpy for oxygen is .

• A. positive
• B. negative
• C. zero

Answer 1

The correct option is A positive

The electron gain enthalpy of an element is defined as the energy liberated when an electron is added to its neutral gaseous atom.
After adding one electron to the oxygen atom, it becomes a uni-negative ion. Due to this, the size of oxygen atom increases and the nuclear force of attraction on the electrons decreases. Also, the new incoming electron experiences repulsion. So, energy has to be supplied to add the second electron. Hence, the second electron gain enthalpy for oxygen is positive.