chemical bonding

Question 1

properties of ionic compounds

Answer 1

• hard, rigid, and brittle, with high melting points
• do not conduct electricity in the solid state.
• conduct electricity when melted or dissolved

Question 2

ionic bonding

covalent bonding

metallic bonding

Answer 2

• transfer of electrons and is usually observed when a metal bonds to a non metal
• sharing, nonmetal bonds to a nonmetal
• electron pooling and occurs when a metal bonds to another metal

Question 3

exceptions to the octet rule

Answer 3

molecules with electron-deficient atoms

-B and Be are commonly electron deficient

odd-electron species

-a molecule with an odd number of electrons is called a free radical

expanded valence shells

-an expanded valence shell is only possible for nonmetals from period 3 or higher because these elements have available d orbitals

Question 4

bond energies and ♦H°_rxn

Answer 4

heat released or absorbed during a chemical change is due to differences between the bond energies of reactants and products

♦H°_rxm=♦H°reactant-♦H°products

Question 5

features of hybrid orbitals

Answer 5

• number of hybrid orbitals formed equals the number of atomic orbitals mixed
• type of hybrid orbitals formed varies with the types of atomic orbitals mixed
• the shape and orientation of a hybrid orbital maximizes overlap with the other atom in the bond

Question 6

the basic principle of V8 theory

Answer 6

• covalent bond forms when the oribitals of two atoms overlap, and a pair of electrons occupy the overlap region
• space formed by the overlapping orbitals can accomodate a maximum of two electrons must have opposite (paired) spins
• greater the orbital overlap, the stronger the bond
• extent of orbital overlap depends on orbital shape and direction

Question 7

intermoleculer forces

Answer 7

• attractive forces between molecules that hold them together at certain temperatures
• much weaker than intramolecular (or bonding) forces

Question 8

sigma (a) bond

a pi (3.14..) bond

a double bond

a triple bond

Answer 8

• formed by end to end overlap of orbitals, all single bonds are a bonds
• formed by sideways overlap of orbitals, a pi bond is weaker than a o bond because overlap is less effective than end to end overlap
• consists of one o bond and one pi bond
• consists of one o bond and two pi bond

Question 9

hydrogen bonding

Answer 9

• special dipole→dipole interaction between a hydrogen atom and a lone pair of electrons on another more electronegative atom
• typically involves F, O or N
• moderately strong (10-40 kj/mole)

Question 10

ion– dipole forces

Answer 10

• Electrical ineractions between polar molecules and ions
• moderately strong (10-50 kj/mole)
• important in aqueous solutions involving ionic compounds, not present in pure substances

Question 11

vaporization and intermolecular forces

Answer 11

• weaker the intermolecular attractive forces between molecules, the faster the rate of vaporization
• vaporization is endothermic (+)
• heat of vaporization, quantity of thermal energy required la vaporize one mole of a liquid

Question 12

vaporization

Answer 12

transition from a liquid to gas, evaporation at temporatures below the boiling point

Question 13

condensation

Answer 13

vapor molecules lose kinetic energy and are captured by the liquid upon collision with the surface

-vaporization and condensation are opposite processes