Question

In the Modern Periodic Table, calcium (atomic number $20$) is surrounded by elements with atomic numbers $12,19,21$ and $38$. Which of these have physical and chemical properties resembling calcium?

Answer 1

The electronic configuration of $Ca\left(20\right)$ is $=2,8,8,2$

Number of valance electrons $=2$

The elements with atomic number $12$ and $38$ both have $2$ valence electrons in their outer shell but elements with $19$ has 1 valance electron and $21$ has $3$ valance electrons. Therefore elements with atomic number $12$ and $38$ have physical and chemical properties resembling calcium.