Unit 2

Question 1

Lattice energy (electrostatic)

Answer 1

the energy required to completely separate
one mole of a solid ionic compound into gaseous ions (E = kQ+Q-/ r)
-Lattice energy (E) increases
as Q increases and/or
as r decreases.

Question 2

covalent bond

Answer 2

chemical bond in which two or more
electrons are shared by two atoms.

Question 3

Polar covalent bond or polar bond

Answer 3

covalent
bond with greater electron density around one of the
two atoms

Question 4

Electronegativity

Answer 4

ability of an atom to attract
toward itself the electrons in a chemical bond
-electron affinity (measurable, Cl highest)
-electronegativity (relative, F highest)

Question 6

Classification of bonds by difference in electronegativity

Answer 6

0-0.4 non-polar covalent
0.5-1.9 polar covalent
2 or > ionic
(dif in electronegativity from sharing, partial transfer, to transfer)

Question 7

Writing Lewis Structures

Answer 7

1. Draw skeletal structure of compound showing
   what atoms are bonded to each other. Put least
   electronegative element in the center.
2. Count total number of valence e-
   . Add 1 for
   each negative charge. Subtract 1 for each
   positive charge.
3. Complete an octet for all atoms except
   hydrogen
4. If structure contains too many electrons, form
   double and triple bonds on central atom as
   needed.

Question 8

formal charge

Answer 8

= total # valence electrons in free atom - nonbonded electrons - 1/2 bonded electrons

Question 9

Formal Charge and Lewis Structures

Answer 9

1. For neutral molecules, a Lewis structure in which there
   are no formal charges is preferable to one in which
   formal charges are present.
2. Lewis structures with large formal charges are less
   plausible than those with small formal charges.
3. Among Lewis structures having similar distributions of
   formal charges, the most plausible structure is the one in
   which negative formal charges are placed on the more
   electronegative atoms.

Question 10

resonance structure i

Answer 10

one of two or more Lewis structures for a single molecule that cannot be represented accurately by
only one Lewis structure. (O3, CO3-2, SO2

Question 11

bond energy

Answer 11

The enthalpy change required to break a particular bond in
one mole of gaseous molecules = BE reactants=BE products

Question 12

bond order

Answer 12

bonds/domains