The set of quantum number for the `19^(th)` electrons in chromium is -

Options

A. 4, 0, 0, `(1)/(2)`
B. 4, 1, `-1, (1)/(2)`
C. 3, 2, 2, `(1)/(2)`
D. 3, 2, `-2, (1)/(2)`

Answer

A

Explanation

`Cr = 1s^(2) 2s^(2) 2p^(6) 3s^(2) 3p^(6) 3d^(5) 4s^(1)`
19th electron enters 4s because 4s is filled earlier than 3d. For `4s, n = 4, l = 0, m = 0, s = + (1)/(2) or - (1)/(2)`