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.

Subtopic:  Lanthanoid & Actinoids Contraction |
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Lanthanoids does not form MO2 among the following is-[M is lanthanoid metal]

1. Pr

2. Dy

3. Nd

4. Yb

Subtopic:  Lanthanoid & Actinoids Contraction |
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