Chemistry Name: ______

Section _____ Chapter 7 Study Guide Date: ______

A. Multiple Choice. 1. Which element is brittle in the solid phase and is a poor conductor of heat and electricity? (1) calcium (2) strontium (3) sulfur (4) copper 2. Which of the following bonds is the least polar in nature?

(1) Cl2 (2) HCl (3) HBr (4) HI 3. Which element in Group VA would most likely have luster and good electrical conductivity? (1) N (2) P (3) Bi (4) As 4. Which electron dot diagram represents an atom of chlorine in the ground state? ...... (1) Cl : (2) . Cl . (3) . Cl . : (4) . Cl. . :

5. Which properties are characteristic of nonmetals? (1) low thermal conductivity and low electrical conductivity (2) low thermal conductivity and high electrical conductivity (3) high thermal conductivity and low electrical conductivity (4) high thermal conductivity and high electrical conductivity 6. Energy is released when the atoms of two elements bond together to form a compound. Compared to the total potential energy of the atoms before bonding, the total potential energy of the atoms after bonding is (1) higher and the compound formed is stable (2) higher and the compound formed is unstable (3) lower and the compound formed is stable (4) lower and the compound formed is unstable 7. Which substance is a conductor of electricity in the liquid phase but not in the solid phase?

(1) Br2 (2) HBr (3) Na (4) NaCl 8. Which kind of energy is stored in a chemical bond? (1) potential energy (2) kinetic energy (3) activation energy (4) ionization energy 9. Polar covalent bonds are caused by (1) unbalanced ionic charges (3) the transfer of electrons between atoms (2) unequal electronegativity values (4) equally shared valence electrons 10. Which type of solid does pure water form when it freezes? (1) ionic (2) network (3) metallic (4) molecular

Created 9 December 2014 B. Short Answer. 1. Indicate whether the following molecules would be polar or nonpolar: a. CS2 nonpolar b. HCN polar 2. Indicate the major type (no intermolecular bonds) of bonding in each of the following: a. HF polar covalent b. NaBr ionic

c. Fe (s) metallic

C. Draw the Lewis structure for the SF4 molecule and give the VSEPR shape, molecular type, molecular geometry, hybridization, and the bonding of the central sulfur atom. . . VSEPR shape: trigonal bipyramidal F ― S ― F Molecule type: AB4E Molecular geometry: see-saw / \ Hybridization: sp3d F F Bonding: 4 σ, 1 lone pair

D. Short Essay:

1. In terms of bond polarity and molecular shape, explain why CO2 is a nonpolar molecule. C = O bonds are polar bonds (∆ electronegativity = 3.4 – 2.6 = 0.8)

CO2 is a linear molecule: O = C = O Since the dipole moments are exactly opposite in a linear molecule, they will cancel exactly leaving the overall molecule nonpolar. 2. Make diagrams that show the structure of a dipole-dipole molecular solid and a metallic solid. Explain why the molecular solid is brittle but the metal is malleable.

Metallic Solid Dipole-Dipole Molecular Solid Metallic solids are held together by a sea of freely moving electrons. If struck by a hammer, any displaced positive ions will still be held together by the fast moving electrons. If a dipole-dipole molecular solid is struck by a hammer, a displacement of any row or column of molecules will cause like charges to be lined up next to one another. The resulting repulsive force will cause the crystal to cleave.

3. Describe or define what a hydrogen bond is and include a diagram that clearly shows the hydrogen bonding in water.

Hydrogen bonds are intermolecular bonds that occur when a hydrogen atom that is polar covalently bonded to a small, highly electronegative atom (N, O, or F) is nearly stripped of its electron density and is therefore strongly attracted to a lone pair of electrons on the N, O, or F atom of the molecule next door.