Transition and Inner Transition Elements — Chemistry STD 12 — Question
Tamilnadu BoardEnglish MediumSTD 12ChemistryTransition and Inner Transition Elements2 Marks
Question
Explain about the causes of lanthanide contraction.
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Answer
1. As we move from one element to another in 4 f series ( Ce to Lu ) the nuclear charge increases by one unit and an additional electron is added into the same inner 4 f sub-shell.
2. 4 f sub-shell have a diffused shapes and therefore the shielding effect of 4 f electrons are relatively poor. Hence, with increase of nuclear charge, the valence shell is pulled slightly towards nucleus.
3. As a result, the effective nuclear charge experienced by the 4 f elelctoms increases and the size of $Ln ^{3+}$ ions decreases.
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