Q.Using VSEPR theory give the shape of the following molecules:
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Start your 14-day free trial to unlock the full solution →VSEPR shape depends on the total number of electron domains (bond pairs + lone pairs) around the central atom: count them, arrange for minimum repulsion, then name the shape traced out by the bonded atoms only (lone pairs affect shape but are not shown in the name).
a) BeCl2:
Central atom Be has 2 bond pairs (to the 2 Cl atoms) and 0 lone pairs (Be has only 2 valence electrons, both used in bonding; it is an exception to the octet rule).
2 electron domains, both bonding => linear geometry, Cl-Be-Cl bond angle = 180 degrees.
b) BCl3:
Central atom B has 3 bond pairs and 0 lone pairs (B has 3 valence electrons, all used in bonding; also an octet exception).
3 electron domains, all bonding => trigonal planar geometry, Cl-B-Cl bond angle = 120 degrees.
c) SF4:
Central atom S has 6 valence electrons; 4 are used to form 4 S-F bond pairs, leaving 1 lone pair. Total 5 electron domains (sp3d hybridisation).
The 5 domains arrange in a trigonal bipyramid; placing the lone pair in an equatorial position (to minimise 90-degree lone-pair/bond-pair repulsions) leaves the 4 bonded F atoms in a distorted, asymmetric arrangement.
Shape (of the atoms) = see-saw (also called distorted tetrahedron).
d) BrF5:
Central atom Br has 7 valence electrons; 5 are used to form 5 Br-F bond pairs, leaving 1 lone pair. Total 6 electron domains (sp3d2 hybridisation).
The 6 domains arrange in an octahedron; the lone pair occupies one of the 6 octahedral positions, leaving the 5 bonded F atoms forming a shape.
Shape = square pyramidal (4 F atoms in a square base, 1 F atom at the apex, lone pair opposite the apex).
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