The elements in which the additional electrons enters (n−2)f orbitals are called inner transition elements. 4f-block elements are also called lanthanides or rare earths so lanthanides are 14 elements in the sixth period (atomic no. =58 to 71 ) that are filling 4f-sublevel. Related Theory Lanthanoid contraction effect results from poor shielding of nuclear charge (nuclear attractive force on electrons) by 4 felectrons so effective nuclear charge increases; the 6s electrons are drawn towards the nucleus, thus resulting in a smaller atomic radius.
Lanthanoids are:
NEET UG 2004 — Chemistry Inorganic Chemistry
2004mcqeasy
Lanthanoids are:
Official previous-year question
Held on 30 Apr 2004 · Verified 9 Jul 2026.
Options
- A
14 elements in the sixth period (atomic no. 90 to 103) that filling of 4f sublevel
- B
14 element in the seventh period (atomic number =90 to 103 ) that are filling 5f sublevel
- C
14 element in the sixth period (atomic number =58 to 71 ) that are filling the 4f sublevel
- D
14 elements in the seventh period (atomic number =50 to 71 ) that are filling 4f sublevel
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