Question

An element with atomic number $21$ is a

• A. halogen
• B. representative element
• C. transition element
• D. alkali metal

Answer 1

Answer: (C)

The electronic configuration of element with atomic number $21$ is

$1s^2,2s^2,2p^6,3s^2,3p^6,4s^2,3d^1$

Since this element contains partly filled $d$ orbital, so it is a $d$ -block element. $d$ -block elements are also known as transition elements.