Which of the following explains the primary cause of lanthanoid contraction?
1. | Greater shielding of 5d electrons by 4f electrons. |
2. | Poor shielding of 5d electrons by 4f electrons. |
3. | Effective shielding of one of the 4f electrons by another in the sub-shell. |
4. | Poor shielding of one 4f electron by another within the sub-shell. |
Lanthanoids does not form MO2 among the following is-[M is lanthanoid metal]
1. Pr
2. Dy
3. Nd
4. Yb