Question

72. Predict the electron pair geometry, the molecular shape, and the bond angle for a carbon tetrabromide molecule, CBra, using VSEPR theory. my VSEPR theory 74. Predict the electron pair geometry, the molecular shape, and the bond angle for a phosphine molecule, PH, using VSEPR theory. ecule even though it has four polar bonds. 78. Apply VSEPR theory to explain why SiF, is a nonpolar molecule even though it has four polar bonds.

Answer 1

Q72)

CBr4

C- central atom has 4 valence electrons used all 4 for bonding with 4 Br. Thus 4 bond pairs, no lone pairs.

Shape and electron pair geometry = TETRAHEDRAL

bond angle 109.5

74) PH3

P has 5 valence electrons and used 3 for bonding with 3 H. Thus 3 bond pairs and one lone pair .

electron pair geometry - TETRAHEDRAL

shape trigonal pyramidal

bond angle - less than 109.5 approximately 95

78)

SiF4 Si has 4 valence electrons and used all 4 for bonding. So 4 bond pairs and no lone pairs.

Shape and electron pair geometry = TETRAHEDRAL

bond angle 109.5

Thus the molecule is symmetrical in shape , so the net bond dipole moment is zero though the bonds are polar.