What does this indicate about their bond angles? (b) The NH 3 molecule is trigonal pyramidal, while BF 3 is trigonal planar. (a) Does this information completely describe the geometry of the molecule? (b) Can you tell how many nonbonding pairs of electrons are around the A atom from this information?ĩ.12 (a) Methane (CH 4) and the perchlorate ion (ClO 4 –) are both described as tetrahedral. MOLECULAR SHAPES THE VSEPR MODEL (sections 9.1 and 9.2)ĩ.11 An AB 2 molecule is described as linear, and the A-B bond length is known. Would you expect them to have a greater atomic orbital contribution from C, have a greater atomic orbital contribution from X, or be an equal mixture of atomic orbitals from the two atoms? (a) Based on the number of electrons, can you determine the identity of X? (b) Would the molecule be diamagnetic or paramagnetic? (c) Consider the π 2 p MOs of the molecule. ĩ.10 The diagram that follows shows the highest-energy occupied MOs of a neutral molecule CX, where element X is in the same row of the periodic table as C. ĩ.9 For each of these contour representations of molecular or-bitals, identify (a) the atomic orbitals ( s or p) used to construct the MO (b) the type of MO (σ or π), (c) whether the MO is bonding or antibonding, and (d) the locations of nodal planes. (a) What is the hybridization at each carbon atom in the molecule? (b) How many σ bonds are there in the molecule? (c) How many π bonds? (d) Identify all the 120° bond angles in the molecule. What type of hybrid orbital is produced in this hybridization?

ĩ.7 The orbital diagram that follows presents the final step in the formation of hybrid orbitals by a silicon atom. (a) To what does an energy of zero correspond in this diagram? (b) According to the valence-bond model, why does the energy decrease as the Cl atoms move from a large separation to a smaller one? (c) What is the significance of the Cl-Cl distance at the minimum point in the plot? (d) Why does the energy rise at Cl-Cl distances less than that at the minimum point in the plot? (e) How can you estimate the bond strength of the Cl-Cl bond from the plot? ĩ.6 In the series SiF 4, PF 3, and SF 2, estimate the F-X-F bond angle in each case and explain your rationale. (a) Based on the structure, how many electron domains surround the C atom in this molecule? (b) Would the molecule have a nonzero dipole moment? (c) If the molecule is polar, in what direction will the overall dipole moment vector point in the molecule? ĩ.5 The following plot shows the potential energy of two Cl atoms as a function of the distance between them. ĩ.4 The molecule shown here is difluoromethane (CH 2F 2), which is used as a refrigerant called R-32.

CHEMISTRY THE CENTRAL SCIENCE 9 MOLECULAR GEOMETRY AND BONDING THEORIES EXERCISESĩ.1 A certain AB 4 molecule has a “seesaw” shape:įrom which of the fundamental geometries shown in Figure 9.3 could you remove one or more atoms to create a molecule having this seesaw shape? ĩ.2 (a) If these three balloons are all the same size, what angle is formed between the red one and the green one? (b) If additional air is added to the blue balloon so that it gets larger, what happens to the angle between the red and green balloons? (c) What aspect of the VSEPR model is illustrated by part (b)? ĩ.3 For each molecule (a)-(f), indicate how many different electron-domain geometries are consistent with the molecular geometry shown.

Hcn molecular geometry ch2f2