Question

The bond angle of $H_{2}Se$ is best described as

• A. Between $109^{\text{o}}$ and $120^{\text{o}}$
• B. Greater than $120^{\text{o}}$
• C. Less than that in $H_{2}S$ but not less than $90^{\text{o}}$
• D. Less than $90^{\text{o}}$

Answer 1

Answer: (C)

According to Drago's rule, when atoms of group 14,15 and 16 (belonging to third period and above) are attached to atoms having Electronegativity less than 2.5, then it has the lone pair of electrons in pure s-orbitals and bond angles are close to $90^o$ . Down the group bond angle of hydrides decreases.
$\angle HXH:\underset{104^o}{H_{2}O}>\underset{92^o}{H_{2}S}>\underset{91^o}{H_{2}Se}>\underset{89.5^o}{H_{2}Te}$