Orbitals

Q. The bond length of $M-C$ bond in metal carbonyls after back-bonding:

1. Increases.
2. Cannot be predicted.
3. Remains constant.
4. Decreases.

Q. Which of the following has highest electron gain enthalpy?
(A) $\left[Ne\right]3s^{2}3p^3$
(B) $\left[Ne\right]3s^{2}3p^4$
(C) $\left[Ne\right]3s^{2}3p^5$
(D) $\left[Ne\right]3s^{2}3p^2$

1. (A)
2. (B)
3. (C)
4. (D)

Q. The impossible overlap among the following is:

1. 
2. 
3. 
4.