Question

Two molecules have the same molecular geometry but different electron domain geometries. Which combination of atoms and lone pairs around the central atom could describe these molecules?
2 atoms and 2 lone pairs; 3 atoms and 0 lone pairs
1 atom and 3 lone pairs; 2 atoms and 1 lone pair
3 atoms and 1 lone pair; 3 atoms and 0 lone pairs
2 atoms and 2 lone pairs; 2 atoms and 1 lone pair

Answer 1

"2 atoms and 2 lone pairs; 2 atoms and 1 lone pair."

Reason: both arrangements have two bonded atoms, so the molecular geometry (positions of the atoms) is bent in both cases. Their electron-domain geometries differ because the total electron domains are 4 (tetrahedral) vs 3 (trigonal planar). Example: H2O (2 bonds, 2 lone pairs — tetrahedral electron geometry, bent molecular geometry) and SO2 (resonance form: 2 bonds, 1 lone pair on S — trigonal planar electron geometry, bent molecular geometry).