Question

The diagonal relationship is shown by certain elements of which periods?

• A. $2^{nd}$ and $3^{rd}$
• B. $3^{rd}$ and $4^{th}$
• C. $4^{th}$ and $5^{th}$
• D. $1^{st}$ and $2^{nd}$

Answer 1

The correct option is A

$2^{nd}$ and $3^{rd}$

$Group1Group2Group3Group4$

$IIPeriod$Li Be B C

$\searrow$ $\searrow$ $\searrow$

$IIIPeriod$Na Mg Al Si

Certain elements of II period show similarity with their diagonal elements in III period.

They show diagonal relationship, Li resembles Mg, Be resembles Al as these pairs of elements have almost identical ionic radius and polarising power. (i.e. charge/size ratio).