Ch 3 - Bonding

Question 1

What are quantum numbers?

Answer 1

describe the size, shape, orientation, and number of atomic orbitals an element posses

Question 2

Principal quantum number?

Answer 2

n

• describes the energy level (shell) in which an electron resides and indicates the distance from the nucleus to the electron
• the possible values range from 1 –>

Question 3

Azimuthal quantum number?

Answer 3

l

• determines the subshell in which an electron resides
• possible values 0 –> n-1
• subshell often indicated with a letter; l=0 is s, 1=p. 2=d. 3=f

Question 4

Magnetic quantum number?

Answer 4

ml

• determines the orbital in which an electron resides
• -l –> +l
• different orbitals have different shapes
• s orbitals: spherical
• p orbitals: dumbbell shaped located on the x, y, or z axis

Question 5

Spin quantum number?

Answer 5

ms
- describes the spin of an electron
+/- 1/2

Question 6

What are bonding orbitals?

Answer 6

created by head to head or tail to tail overlap of atomic orbitals of the same sign and are energetically favorable

Question 7

What are antibonding orbitals?

Answer 7

created by head to head or tail to tail overlap of atomic orbitals that have opposite signs and are energetically unfavorable

Question 8

How many electrons do sigma bonds have?

Answer 8

they are single bonds that have 2 electrons

Question 9

What is a pi bond?

Answer 9

created by sharing of electrons between 2 un hybridized p orbitals that align side by side

Question 10

What bonds are in double bonds? triple bonds?

Answer 10

• double: 1 sigma an 1 pi bond

- triple: 1 sigma and 2 pi bonds

Question 11

How do single bonds compare to multiple bonds?

Answer 11

• multiple bonds are less flexible than single bonds because rotations is not permitted in the presence of a pi bond
• multiple bonds are shorter and stronger than single bonds, although individual pi bonds are weaker than sigma bonds

Question 12

What characters do sp3 hybridization have? What shape do they form? Which carbons are sp3?

Answer 12

• have 25% s character and 75% p character
• tetrahedral geometry with 109.5 bond angles
• carbons with all single bonds

Question 13

What characters do sp2 hybridization have? What shape do they form? Which carbons are sp2?

Answer 13

• 33% s character and 67% p character
• trigonal planar geometry with 120 bond angles
• carbons with one double bond

Question 14

What characters do sp hybridization have? What shape do they form? Which carbons are sp?

Answer 14

• 50% s character and 50% p character
• linear geometry with 180 bond angles
• carbons with a triple bond or 2 double bonds

Question 15

What is resonance?

Answer 15

describes the delocalization of electrons in molecules that have conjugated bonds
- increases the stability of a molecule

Question 16

When does conjugation occur?

Answer 16

when single and multiple bonds alternate, creating a system of un hybridized p orbitals down the backbone of the molecule through which pi bonds can delocalize

Question 17

What do the various resonance forms contribute and when are they favored?

Answer 17

• contribute to the true electron density of the molecule, the more stable the resonance forms, the more it contributes
• favored if they lack formal charge, form full octets on electronegative atoms, or stabilize charges through induction and aromaticity