The dand fblock elements - Result Question 78
####78. Lanthanoids are
[2004]
(a) 14 elements in the sixth period (atomic no. $=90$ to 103) that are filling $4 f$ sublevel
(b) 14 elements in the seventh period (atomic no. $=90$ to 103) that are filling $5 f$ sublevel
(c) 14 elements in the sixth period (atomic no. $=58$ to 71 ) that are filling $4 f$ sublevel
(d) 14 elements in the seventh period (atomic no. $=58$ to 71 ) that are filling $4 f$ sub level
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Solution:
- (c) Lanthanides are $4 f$-series elements starting from cerium $(Z=58)$ to lutetium $(Z=71)$. These are placed in the sixth period and in third group.
