Question

An element with atomic number $21$ is a

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

Answer 1

Answer: (C)

transition element

Answer 2

The electronic configuration of element with atomic number $21$ is $1 s^{2}, 2 s^{2}, 2 p^{6}, 3 s^{2}, 3 p^{6}, 4 s^{2}, 3 d^{1}$ Since this element contains partly filled $d$ orbital, so it is a $d$ -block element. $d$ -block elements are also known as transition elements.