Question

There are two rows of inner-transition elements in the periodic table each containing 14 elements. The reason for this may be:

• A. f-Orbital has seven values for magnetic quantum number, hence total electrons are 14
• B. In the periodic table, there is space to accommodate 14 electrons only
• C. Only 28 inner-transition elements have been discovered till date
• D. 28 is the maximum number of elements that any block can accommodate

Answer 1

The correct option is A f-Orbital has seven values for magnetic quantum number, hence total electrons are 14

For f-orbital, $l=3$

$m_l=2l+1=7$

There are $7$ electrons with $+\frac{1}{2}$ spin and $7$ electrons with $-\frac{1}{2}$ spin. Hence, total electrons are $14$.
Hence, Correct option is (a).