Chapter 3, Problem 63P

3-79 Answer true or false.

(a) The letters VSEPR stand for valence-shell electron-pair repulsion.

(b) In predicting bond angles about a central atom in a covalent molecule, the VSEPR model considers only shared electron pairs (electron pairs involved in forming covalent bonds).

(c) The VSEPR model treats the two electron pairs of a double bond as one region of electron density and the three electron pairs of a triple bond as one region of electron density.

(d) In carbon dioxide, OCO, carbon is surrounded by four pairs of electrons and the VSEPR model predicts 109.5° for the O−C−O bond angle.

(e) For a central atom surrounded by three regions of electron density, the VSEPR model predicts bond angles of 120°.

(f) The geometry about a carbon atom surrounded by three regions of electron density is described as trigonal planar.

(g) For a central atom surrounded by four regions of electron density, the VSEPR model predicts bond angles of 360°/4 = 90°.

(h) For the ammonia molecule, NH₃, the VSEPR model predicts H−N−H bond angles of 109.5°.

(i) For the ammonium ion, NH₄, the VSEPR model predicts H−N−H bond angles of 109.5°.

(j) The VSEPR model applies equally well to covalent compounds of carbon, nitrogen, and oxygen.

(k) In water, H−O−H, the oxygen atom forms covalent bonds to two other atoms, and therefore, the VSEPR model predicts an H−O−H bond angle of 180°.

(l) If you fail to consider unshared pairs of valence electrons when you use the VSEPR model, you will arrive at an incorrect prediction.

(m) Given the assumptions of the VSEPR model, the only bond angles it predicts for compounds of carbon, nitrogen, and oxygen are 109.5°, 120°, and 180°.