In the ground state, an element has 13 electrons in $\mathrm{M}$ shell. The element is

In the ground state, an element has 13 electrons in $\mathrm{M}$ shell. The element is
  1. copper
  2. chromium
  3. nickel
  4. iron

Solution

$M$ shell $=3$ rd shell Electronic configuration $=1 s^2, 2 s^2, 2 p^6, 3 s^2, 4 s^1, 3 d^5$ Number of $e^{-}$in 3rd shell $=3 s^2, 3 p^6, 3 d^5$ $=2+6+5=13$ Total $e^{-}=24$ So, the element is $\mathrm{Cr}$.

Asked in: AP EAMCET 2001

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