Question

The correct order of electron gain enthalpy (magnitude only) for group 16 elements is:

• A. \( \mathrm{Te>Se>S>O} \)
• B. \( \mathrm{S>Se>Te>O} \)
• C. \( \mathrm{O>S>Se>Te} \)
• D. \( \mathrm{S>O>Se>Te} \)

Hint:

Remember:
Oxygen has lower electron gain enthalpy than sulfur due to strong inter-electronic repulsion.
Always check for exceptions involving small atoms like O and F.

Answer 1

The Correct Option is B

The question asks for the correct order of electron gain enthalpy (in terms of magnitude) for group 16 elements. To understand this, let's first explore the concept of electron gain enthalpy.

Electron Gain Enthalpy: It is the energy change when an electron is added to an isolated gaseous atom to form an anion. A more negative value of electron gain enthalpy indicates a greater tendency of an atom to accept an electron.

As we move down the group in the periodic table for group 16 elements (which include Oxygen (O), Sulfur (S), Selenium (Se), and Tellurium (Te)), there are several factors to consider:

• Atomic Size: It increases down the group, resulting in a decrease in the force of attraction between the added electron and the nucleus.
• Nuclear Charge: While the nuclear charge increases down the group, the increasing atomic size generally has a more significant impact, leading to a less negative electron gain enthalpy.

Now let's consider each option: 

1. \(\mathrm{Te>Se>S>O}\): Incorrect. Tellurium, being heavier, should have the least magnitude of electron gain enthalpy compared to the other members.
2. \(\mathrm{S>Se>Te>O}\): Correct. Sulfur has a highly negative electron gain enthalpy in comparison to the others. Oxygen, despite having a smaller size, has less electron gain enthalpy due to increased electron-electron repulsion in its compact 2p subshell.
3. \(\mathrm{O>S>Se>Te}\): Incorrect. While oxygen might be expected to have a stronger electron gain enthalpy due to its size, the repulsion between electrons in its orbitals makes its enthalpy less negative than sulfur.
4. \(\mathrm{S>O>Se>Te}\): Incorrect. While sulfur indeed has a more negative electron gain enthalpy than oxygen, as discussed previously, selenium and tellurium should follow sulfur.

Conclusion: Based on the above analysis, the correct order for the magnitude of electron gain enthalpy for group 16 elements is \(\mathrm{S>Se>Te>O}\).