Question

draw the lewis structure of nitrous acid (hno₂) and then choose the appropriate pair of molecular geometries of the two central atoms. your answer choice is independent of the orientation of your drawn structure.
a bent (109.5°)/bent (120°)
b bent (109.5°)/tetrahedral
c bent (109.5°)/planar
d trigonal planar/bent (109.5°)
e bent (120°)/planar

Explanation:

Step1: Calculate valence - electrons

Nitrous acid is HNO₂. H has 1 valence - electron, N has 5 valence - electrons, and O has 6 valence - electrons. So the total number of valence - electrons is 1 + 5+2×6 = 18 electrons.

Step2: Determine the central atoms

The central atoms in HNO₂ are N and one of the O atoms. Connect the atoms with single bonds first: H - O - N - O. This uses 6 electrons, leaving 18 - 6=12 electrons as lone - pairs.

Step3: Distribute lone - pairs and form multiple bonds

Place lone - pairs on the atoms to satisfy the octet rule. The N atom needs to form a double bond with one of the O atoms to have an octet.

Step4: Determine molecular geometries

For the N atom: It has 3 electron - groups (2 single bonds and 1 double bond), so its electron - group geometry is trigonal planar and molecular geometry is bent with bond angles close to 120°. For the O atom bonded to H: It has 4 electron - groups (2 single bonds and 2 lone - pairs), so its electron - group geometry is tetrahedral and molecular geometry is bent with bond angles close to 109.5°.

Answer:

A. bent (109.5°)/ bent (120°)