Unit 4: Bonding: VSEPR And Molecular Orbitals

Question 1

What does VSEPR stand for?

Answer 1

Valence Shell Electron Pair Repulsion.

Question 2

What does VSEPR theory predict?

Answer 2

The 3D shape of molecules based on repulsion between electron groups.

Question 3

Why do electron groups repel each other?

Answer 3

Because they are negatively charged and want to be as far apart as possible.

Question 4

What determines molecular geometry in VSEPR theory?

Answer 4

The number and types of electron groups (bonds and lone pairs).

Question 5

How many basic electron group geometries are there?

Answer 5

Five.

Question 6

What is the electron group geometry for 2 electron groups?

Answer 6

Linear.

Question 7

What is the electron group geometry for 3 electron groups?

Answer 7

Trigonal planar.

Question 8

What is the electron group geometry for 4 electron groups?

Answer 8

Tetrahedral.

Question 9

What is the electron group geometry for 5 electron groups?

Answer 9

Trigonal bipyramidal.

Question 10

What is the electron group geometry for 6 electron groups?

Answer 10

Octahedral.

Question 11

What is the molecular geometry when all electron groups are bonding?

Answer 11

Same as electron group geometry.

Question 12

What effect do lone pairs have on bond angles?

Answer 12

They reduce the bond angles.

Question 13

Do lone pairs repel more or less than bonding pairs?

Answer 13

More.

Question 14

What is the shape of CH4?

Answer 14

Tetrahedral.

Question 15

What is the shape of NH3?

Answer 15

Trigonal pyramidal.

Question 16

What is the shape of H2O?

Answer 16

Bent.

Question 17

What is molecular polarity?

Answer 17

A measure of the overall dipole in a molecule.

Question 18

What two factors determine molecular polarity?

Answer 18

Bond polarity and molecular geometry.

Question 19

What is a dipole moment?

Answer 19

A vector quantity representing bond polarity.

Question 20

What causes a molecule to be nonpolar?

Answer 20

Symmetric distribution of polar bonds (vector cancellation).

Question 21

What is valence bond theory?

Answer 21

A model that explains bonding using orbital overlap.

Question 22

What causes a covalent bond in valence bond theory?

Answer 22

Overlap of half-filled atomic orbitals.

Question 23

What is hybridization?

Answer 23

The mixing of atomic orbitals to form new, hybrid orbitals.

Question 24

What is the hybridization of a tetrahedral atom?

Answer 24

sp3.

Question 25

What is the hybridization of a trigonal planar atom?

Answer 25

sp2.

Question 26

What is the hybridization of a linear atom?

Answer 26

sp.

Question 27

What is a sigma (σ) bond?

Answer 27

A bond with electron density along the bond axis; allows rotation.

Question 28

What is a pi (π) bond?

Answer 28

A bond formed by sideways overlap; no free rotation.

Question 29

What kind of bond does every single bond include?

Answer 29

A sigma bond.

Question 30

What kind of bonds are in a double bond?

Answer 30

One sigma and one pi bond.

Question 31

What kind of bonds are in a triple bond?

Answer 31

One sigma and two pi bonds.

Question 32

What hybridization allows for expanded octets (5 electron groups)?

Answer 32

sp3d.

Question 33

What hybridization allows for 6 electron groups?

Answer 33

sp3d2.

Question 35

What is the main difference between valence bond theory and molecular orbital (MO) theory?

Answer 35

Valence bond theory assigns electrons to specific atoms and bonds; MO theory assigns electrons to orbitals spread across the entire molecule.

Question 36

How are molecular orbitals formed?

Answer 36

By the mathematical addition and subtraction of atomic orbitals, resulting in bonding and antibonding MOs.

Question 37

What is a bonding molecular orbital?

Answer 37

An orbital formed by constructive interference of atomic orbitals, with high electron density between nuclei and lower energy.

Question 38

What is an antibonding molecular orbital?

Answer 38

An orbital formed by destructive interference of atomic orbitals, with a node between nuclei and higher energy.

Question 39

What is the formula for bond order in MO theory?

Answer 39

Bond order = (number of bonding electrons - number of antibonding electrons) / 2

Question 40

What does a bond order of 0 mean?

Answer 40

No bond is likely to form between the atoms.

Question 41

What is the HOMO in an MO diagram?

Answer 41

The highest occupied molecular orbital.

Question 42

What is the LUMO in an MO diagram?

Answer 42

The lowest unoccupied molecular orbital.

Question 43

What property is associated with unpaired electrons in MO diagrams?

Answer 43

Paramagnetism.

Question 44

How many electrons can each molecular orbital hold?

Answer 44

2 electrons with opposite spins.

Question 45

What are intermolecular forces (IMFs)?

Answer 45

Attractive forces between molecules that affect physical properties like boiling point and melting point.

Question 46

What are the three main types of intermolecular forces?

Answer 46

Dispersion forces, dipole-dipole interactions, and hydrogen bonding.

Question 47

What causes dispersion forces?

Answer 47

Temporary dipoles caused by shifting electron clouds in molecules.

Question 48

What factors increase the strength of dispersion forces?

Answer 48

Larger molecular size, more electrons, and greater surface area.

Question 49

What molecules experience dipole-dipole forces?

Answer 49

Polar molecules with permanent dipoles.

Question 50

What is hydrogen bonding?

Answer 50

A strong dipole-dipole interaction between hydrogen and N, O, or F atoms.

Question 51

How do IMFs affect boiling point?

Answer 51

Stronger IMFs increase boiling point.

Question 52

How do IMFs affect melting point?

Answer 52

Stronger IMFs increase melting point.

Question 53

How do IMFs affect solubility?

Answer 53

Substances with similar IMFs are more likely to dissolve each other ('like dissolves like').

Question 54

Which IMF is the weakest?

Answer 54

Dispersion forces.

Question 55

Which IMF is the strongest?

Answer 55

Hydrogen bonding.