Chapter 10

Question 1

When is the system more stable, as potential energy gets more negative or positive?

Answer 1

The more negative, the more stable the system becomes

Question 2

Lewis Theory

Answer 2

Positions of electrons in the molecule are NOT considered; quickest bonding theory to employ

Question 3

Valence-bond Theory

Answer 3

Atomic orbitals overlap where electrons are shared

Atomic orbitals are averaged to give geometries (VSEPR)

Question 4

Molecular Orbital Theory

Answer 4

Explains bond order, stability, magnetism, resonance

Question 5

Ionic Compounds

Answer 5

Metal to non-metal ionic interaction

Question 6

Covelant Bonds

Answer 6

Sharing of electrons between two nonmetal atoms

Question 7

Octet Rule

Answer 7

Electrons are transferred or shared to give each atom a noble gas configuration

Question 8

Coordinate Covalent Bond

Answer 8

When a single atom contributes both of the electrons to the bond

Question 9

Writing Lewis Structures

Answer 9

1. Find total # of valence electrons (add for anions and subtract for cations)
2. Choose central and terminal atoms
3. Draw two electrons between each pair of connected atoms
4. Add lone pairs to outer atoms (except H) to give complete octets
5. Place all remaining electrons in lone pairs on central atom

Question 10

Formal Charges

Answer 10

Used to keep track of how electrons are shared

FC = # valence electrons in central atom - lone electrons - # bond pairs

Question 11

Resonance

Answer 11

When two or more Lewis Structures are equally feasible

Question 12

Exceptions to Octet Rule

Answer 12

Odd-electron species (Radicals), Incomplete Octets (Boron, Hydrogen), expanded valence shells (period 3 and up)

Question 13

Polarity of Bonds

Answer 13

non-polar when the shared electrons are equally attracted to both atoms
Polar - shared electrons are more strongly attracted to an atom

Question 14

Electronegativity

Answer 14

Ability of an atom to attract electrons in a covalent bond
Higher values for electronegativity indicate greater attraction
Non-metals have higher EN than metals
EN rises going right and up the periodic table

Question 15

Electronegativity and Polarity of Bonds

Answer 15

If difference in EN is small = non-polar
If difference is intermediate = polar
If difference is large = ionic bond

Question 16

Dipole Moment

Answer 16

Product of a partial charge and distance

Draw arrow towards the atom with the higher EN

Question 17

How to assign VSEPR

Answer 17

1. Draw Lewis Structure
2. Count # of electron groups (each lone pair counts as 1, each bond group is 1 even if double)
3. Predict molecular shape and state VSEPR

Question 18

Electron and Molecular Geometry - Linear

Answer 18

Two charge clouds/electron groups
Electron geom = Linear
Molecular geom = Linear
Bond angle = 180
VSEPR = AX2

Question 19

Electron and Molecular Geometry - Trigonal Planar

Answer 19

Three charge clouds/electron groups
*Three outer atoms + no lone pairs
Molecular geom = Trigonal Planar
Bond angle = 120
VSEPR = AX3
*Two outer atoms + one lone pair
Molecular geom = Bent
Bond angle = 120
VSEPR = AX2E

Question 20

Electron and Molecular Geometry - Tetrahedral

Answer 20

Four charge clouds/electron groups
*Four outer atoms + no lone pairs
Molecular geom = Tetrahedral
Bond angle = 109.5
VSEPR = AX4
*Three outer atoms + one lone pair
Molecular geom = Trigonal-pyramidal
Bond angle = 109.5
VSEPR = AX3E
*Two outer atoms + two lone pairs
Molecular geom = Bent
Bond angle = 109.5
VSEPR = AX2E2

Question 21

Electron and Molecular Geometry - Trigonal-bipyramidal

Answer 21

Five charge clouds/electron groups
*Five outer atoms + no lone pairs
Molecular geom = trigonal bipyramidal
Bond angle = 90, 120
VSEPR = AX5
*Four outer atoms + one lone pair
Molecular geom = see-saw
Bond angle = 90, 120
VSEPR = AX4E
*Three outer atoms + two lone pairs
Molecular geom = T-shaped
Bond angle = 90
VSEPR = AX3E2
*Two outer atoms + three lone pairs
Molecular geom = Linear
Bond angle = 180
VSEPR = AX2E3

Question 22

Electron and Molecular Geometry - Octahedral

Answer 22

Six charge clouds/electron groups
*Six outer atoms + no lone pairs
Molecular geom = Octahedral
Bond angle = 90
VSEPR = AX6
*Five outer atoms + one lone pair
Molecular geom = square-pyramidal
Bond angle = 90
VSEPR = AX5E
*Four outer atoms + two lone pairs
Molecular geom = Square-planar
Bond angle = 90
VSEPR = AX4E2

Question 23

Bond Order

Answer 23

Single bond = 1
Double bond = 2
Triple bond = 3
*Bond length decreases with increasing bond order

Question 24

Bond Dissociation Energies

Answer 24

Energy required to break one mole of covalent bonds for gaseous species

• Energy is release when bonds form; energy absorbed when bonds break
• Use changes of enthalpy reactions to calculate energy for bonds (Hess’ Law)