Chemistry Module 2 - Bonding and Structure (part 2 - part 1 is in flashcards)

Question 1

What is electronegativity?

Answer 1

Electronegativity is the ability of an atom to attract bonding electrons in a covalent bond towards itself.

Question 2

What factors affect electronegativity?

Answer 2

1. Nuclear Charge
2. Atomic Radius
3. Electron shielding

Question 3

What happens to electronegativity, across periods, and why?

Answer 3

Electronegativity increases across periods (due to smaller atomic radius and greater nuclear charge)

Question 4

What happens to electronegativity, down groups, and why?

Answer 4

Electronegativity decreases down groups (due to increased shielding and larger atomic radius).

Question 5

What are the most electronegative elements?

Answer 5

HINT: FONCL

Fluorine
Oxygen
Nitrogen
Chlorine

Question 6

How can electronegativity be measured?

Answer 6

Electronegativity can be measured using the Pauling scale, with fluorine having the highest value of 4.0.

Question 7

How does the electronegativity difference affect bond polarity?

Answer 7

A larger electronegativity difference results in greater bond polarity, leading to a greater ionic character.

Question 8

What are the extremes in bonding types?

Answer 8

The extremes are ionic bonds (high electronegativity difference) and covalent bonds (low or no difference).

Question 9

What is a permanent dipole?

Answer 9

A permanent dipole occurs when two atoms with different electronegativities form a polar bond, creating a slightly negative and slightly positive region.

Question 10

Give an example of a molecule with a permanent dipole.

Answer 10

Hydrogen fluoride (HF) has a permanent dipole because fluorine is more electronegative than hydrogen, pulling electrons towards itself.

Question 11

What makes a molecule polar?

Answer 11

A molecule is polar if it has polar bonds with dipoles that do not cancel out due to the molecule’s shape.

Question 12

Why is CO₂ non-polar despite having polar bonds?

Answer 12

CO₂ is non-polar because its linear shape causes the dipoles to cancel out.

Question 13

How can polar molecules form a lattice?

Answer 13

Polar molecules with permanent dipoles can align to form a lattice, similar to the arrangement of ions in an ionic lattice.

Question 14

What is an induced dipole?

Answer 14

An induced dipole occurs when the distribution of electrons in a molecule is influenced by nearby atoms or molecules.

Question 15

What are London forces?

Answer 15

London forces (or dispersion forces) are a type of induced dipole-dipole interaction that occurs due to temporary shifts in electron density.

Question 16

What are the three main types of intermolecular forces?

Answer 16

The three main types are Van der Waals forces, dipole-dipole interactions, and hydrogen bonds.

Question 17

What are Van der Waals forces?

Answer 17

Van der Waals forces are weak induced dipole-dipole interactions that occur between molecules.

Question 18

What factors affect the strength of Van der Waals forces?

Answer 18

The strength increases with molecular size (larger molecules have more electrons) and the shape (straight-chain molecules have stronger forces than branched molecules).

Question 19

How do Van der Waals forces affect boiling points?

Answer 19

Stronger Van der Waals forces result in higher boiling points due to the greater energy required to break the forces.

Question 20

What are permanent dipole-dipole interactions?

Answer 20

Permanent dipole-dipole interactions occur between molecules with permanent dipoles, where the positive end of one molecule attracts the negative end of another.

Question 21

How do permanent dipole-dipole interactions compare to London forces?

Answer 21

Permanent dipole-dipole interactions are stronger than London forces, so more energy is needed to overcome them.

Question 22

What is hydrogen bonding?

Answer 22

Hydrogen bonding occurs when hydrogen is bonded to highly electronegative atoms (N, O, or F), forming a weak attraction with a lone pair of electrons on another electronegative atom.

Question 23

Which elements are involved in hydrogen bonding?

Answer 23

Hydrogen bonds form between hydrogen and nitrogen (N), oxygen (O), or fluorine (F).

Question 24

Why does water have unusual properties like a high boiling point?

Answer 24

Water has hydrogen bonds, which are strong intermolecular forces requiring more energy to overcome, leading to a higher boiling point than expected for a small molecule.

Question 25

Why is ice less dense than liquid water?

Answer 25

Hydrogen bonds in ice form a rigid structure, holding water molecules farther apart and creating air gaps, which lowers its density.

Question 26

How do ionic and covalent compounds compare in terms of boiling and melting points?

Answer 26

Ionic compounds generally have higher boiling and melting points due to strong electrostatic attractions between ions, compared to the weaker forces in covalent compounds.

Question 27

How does molecular size affect boiling points?

Answer 27

Larger molecules have higher boiling points because they have more electrons, which increases London forces and the energy required to overcome them.

Question 28

How does branching affect boiling points?

Answer 28

Branching reduces the boiling point because branched molecules cannot pack as closely together as straight-chain molecules, leading to weaker Van der Waals forces.

Question 29

How does molecular mass influence London dispersion forces?

Answer 29

As molecular mass increases, the size of the electron cloud increases, leading to stronger London forces and higher boiling and melting points.

Question 30

Which intermolecular forces are the strongest?

Answer 30

Hydrogen bonds are the strongest, followed by permanent dipole-dipole interactions, and then London dispersion forces, which are the weakest.

Question 31

What are the key properties of metals due to metallic bonding?

Answer 31

Metals are good conductors of electricity (due to delocalized electrons), have high melting/boiling points, and are malleable and ductile because the layers of metal ions can slide over each other without breaking the bond.

Question 31

Why is ice less dense than liquid water?

Answer 31

Ice is less dense because hydrogen bonds in ice form a rigid structure, holding the water molecules farther apart and creating more air gaps.

Question 32

How do intermolecular forces affect physical properties like boiling and melting points?

Answer 32

Stronger intermolecular forces lead to higher boiling and melting points. For example, water has a high boiling point due to hydrogen bonding, while methane, with weaker London forces, has a lower boiling point.

Question 32

What is metallic bonding?

Answer 32

Metallic bonding occurs between metal atoms. Electrons in the outer shells are delocalized, forming a “sea” of electrons that move freely. This explains properties like electrical conductivity and malleability.

Question 33

How does polarity affect solubility?

Answer 33

Polar substances tend to dissolve in polar solvents, while non-polar substances dissolve in non-polar solvents. For example, water (polar) dissolves salts (polar) but not oils (non-polar).

Question 33

Can you give an example of a polar and a non-polar molecule?

Answer 33

Water (H₂O) is polar because of its bent shape and the unequal sharing of electrons between oxygen and hydrogen. Carbon dioxide (CO₂) is non-polar because its linear shape causes the dipoles to cancel out.

Question 34

How does the shape of a molecule affect its polarity?

Answer 34

The shape of a molecule determines whether dipoles cancel out or not. In a symmetrical molecule (like CO₂), dipoles cancel out, making it non-polar. In an asymmetrical molecule (like H₂O), dipoles don’t cancel out, making it polar.

Question 35

How do intermolecular forces affect physical properties like boiling and melting points?

Answer 35

Stronger intermolecular forces (e.g., hydrogen bonds) lead to higher boiling and melting points. For example, water has a high boiling point due to strong hydrogen bonds, compared to methane, which has weaker London forces.

Question 36

How do intermolecular forces influence viscosity?

Answer 36

Stronger intermolecular forces, such as hydrogen bonds, result in higher viscosity. For example, honey (which has strong intermolecular forces) is more viscous than water.

Question 37

How do intermolecular forces influence surface tension?

Answer 37

Stronger intermolecular forces lead to higher surface tension. Water has high surface tension due to hydrogen bonding, which allows it to form droplets.