3 Bonding

Question 1

quantum numbers

Answer 1

size, shape, number, orientation or atomic orbitals in an element

Question 2

principal quantum number (n)

Answer 2

energy level of given electron shell

measure of size

energy increases as “n” increases

Question 3

azimuthal quantum number (l)

Answer 3

electron subshell

0 to n-1

0 = s
1 = p
2 = d
3 = f

energy increases as “l” increases

Question 4

magnetic quantum number (ml)

Answer 4

orbitals (shape)

-“l” to “l”

Question 5

spin quantum number (ms)

Answer 5

each orbital can hold 2 electrons

+/- (1/2)

Question 6

molecular orbitals

Answer 6

when 2 atomic orbitals combine

add/subtract wave functions

Question 7

bonding molecular orbital

Answer 7

if signs of the wave functions are the same

lower-energy (more stable)

Question 8

antibonding molecular orbital

Answer 8

if signs of wave functions are different

higher-energy (less stable)

Question 9

sigma bond

Answer 9

head-to-head/tail-to-tail overlap

allow free rotation about axis

all single bonds

Question 10

pi bond

Answer 10

when 2 p-orbitals line up in parallel, electron clouds overlap
bonding MO forms

hinder rotation, lock atoms in place

cannot exist independently of a sigma bond

Question 11

1 pi bond on existing sigma bond

Answer 11

double bond

Question 12

2 pi bonds on existing sigma bond

Answer 12

triple bond

Question 13

individual pi bonds are _______ (stronger/weaker) than individual sigma bonds

Answer 13

weaker

Question 14

hybrid orbitals

Answer 14

mixing different kinds of orbitals; hybridization

Question 15

sp3 hybrid orbitals

Answer 15

3 p-orbitals + 1 s-orbital
75% p character + 25% s character

tetrahedral geometry

Question 16

sp2 hybrid orbitals

Answer 16

1 s-orbital + 2 p-orbitals
33% s character + 67% p character

trigonal planar geometry (120º apart)

Question 17

What is the function of the unhybridized 3rd p-orbital in sp2 hybridization?

Answer 17

participates in pi bond (alkenes)

Question 18

sp hybrid orbitals

Answer 18

1 s-orbital + 1 p-orbital
50% s character + 50% p character

linear geometry (180º apart)

Question 19

What is the function of the 2 unhybridized p-orbitals in sp hybridization?

Answer 19

2 double bonds –> triple bond (alkynes)

Question 20

conjugation

Answer 20

alternating single and multiple bonds

aligns a number of unhybridized p-orbitals down the backbone of a molecule

pi electron destabilization

• -> adds stability
• -> electron density distributed throughout structure

Question 21

“true hybrid” of resonance structures

Answer 21

no equilibrium

more stable resonance forms contribute more to the “true hybrid” form