3.1.3 Bonding

Question 1

What is ionic bonding?

Answer 1

Ionic bonding is the electrostatic attraction between oppositely charged ions. It forms when electrons are transferred from a metal to a non-metal, creating a lattice of ions with strong attractions between them.

Question 2

How are compound ions included in ionic bonding?

Answer 2

Compound ions, such as SO4^2− (sulfate), OH^− (hydroxide), NO3^− (nitrate), CO3^2− (carbonate), and NH4^+ (ammonium), participate in ionic bonding by combining with oppositely charged ions to form neutral ionic compounds.

Question 3

How do you predict the charge of an ion from the Periodic Table?

Answer 3

Group number often indicates ion charge: Group 1 → +1, Group 2 → +2, Group 6 → −2, Group 7 → −1. Transition metals may form multiple ions.

Question 4

How do you construct a formula for an ionic compound?

Answer 4

Balance the total positive and negative charges of the ions so the compound is neutral. E.g., Mg^2+ and Cl^− → MgCl2.

Question 5

What is a covalent bond?

Answer 5

A covalent bond is a shared pair of electrons between two non-metal atoms. Each atom contributes one electron to the shared pair.

Question 6

What is a multiple covalent bond?

Answer 6

A bond in which more than one pair of electrons is shared. Double bonds involve two shared pairs (e.g., O2), and triple bonds involve three shared pairs (e.g., N2).

Question 7

What is a dative covalent (coordinate) bond?

Answer 7

A covalent bond where both electrons in the shared pair come from the same atom. Represented with an arrow pointing from the donor atom to the acceptor.

Question 8

How is a covalent bond represented in diagrams?

Answer 8

As a straight line (–) between atoms.

Question 9

How is a coordinate bond represented?

Answer 9

With an arrow (→) from the atom donating the lone pair to the atom accepting it.

Question 10

What is metallic bonding?

Answer 10

Metallic bonding is the electrostatic attraction between positive metal ions and a sea of delocalised electrons. These electrons are free to move throughout the structure.

Question 11

How does metallic bonding affect the properties of metals?

Answer 11

It gives metals high melting and boiling points, electrical conductivity, malleability, and ductility due to strong bonds and mobile electrons.

Question 12

What are the four types of crystal structure?

Answer 12

Ionic, metallic, molecular (simple covalent), and macromolecular (giant covalent). Each has different bonding and physical properties.

Question 13

Give examples of each crystal structure type.

Answer 13

Ionic: NaCl; Metallic: Mg; Molecular: I2, ice; Macromolecular: diamond, graphite, SiO2.

Question 14

Why do ionic compounds have high melting points and conduct when molten?

Answer 14

Strong electrostatic forces between ions require high energy to break. When molten, ions are free to move and carry charge.

Question 15

Why do molecular compounds have low melting and boiling points?

Answer 15

They have weak intermolecular forces (e.g., van der Waals, dipole-dipole, hydrogen bonding) which require less energy to overcome.

Question 16

Why do giant covalent structures have high melting points?

Answer 16

All atoms are held together by strong covalent bonds in a giant lattice, requiring lots of energy to break.

Question 17

Why does graphite conduct electricity but diamond does not?

Answer 17

Graphite has delocalised electrons between layers that can move. Diamond has no free electrons; all are involved in covalent bonding.

Question 18

What happens to energy during changes of state?

Answer 18

Energy is absorbed when bonds are broken (melting, boiling) and released when bonds form (condensation, freezing).

Question 19

What determines molecular shape according to VSEPR theory?

Answer 19

Electron pairs around the central atom repel each other and arrange as far apart as possible to minimise repulsion. Both bonding and lone pairs count.

Question 20

How do lone pairs affect bond angles?

Answer 20

Lone pair–lone pair repulsion > lone pair–bond pair > bond pair–bond pair, meaning lone pairs reduce bond angles more.

Question 21

What is the shape and bond angle of a molecule with 2 bonding pairs and 0 lone pairs?

Answer 21

Linear, 180° (e.g., BeCl2).

Question 22

What is the shape and bond angle of a molecule with 3 bonding pairs and 0 lone pairs?

Answer 22

Trigonal planar, 120° (e.g., BF3).

Question 23

What is the shape and bond angle of a molecule with 4 bonding pairs and 0 lone pairs?

Answer 23

Tetrahedral, 109.5° (e.g., CH4).

Question 24

What is the shape and bond angle of a molecule with 3 bonding pairs and 1 lone pair?

Answer 24

Pyramidal, ~107° (e.g., NH3).

Question 25

What is the shape and bond angle of a molecule with 2 bonding pairs and 2 lone pairs?

Answer 25

Bent (V-shaped), ~104.5° (e.g., H2O).

Question 26

What is the shape and bond angle of a molecule with 5 bonding pairs and 0 lone pairs?

Answer 26

Trigonal bipyramidal, 90° and 120° (e.g., PCl5).

Question 27

What is the shape and bond angle of a molecule with 6 bonding pairs and 0 lone pairs?

Answer 27

Octahedral, 90° (e.g., SF6).

Question 28

What is electronegativity?

Answer 28

The ability of an atom to attract the bonding pair of electrons in a covalent bond.

Question 29

What causes bond polarity?

Answer 29

A difference in electronegativity between bonded atoms causes unequal sharing of electrons, leading to a polar bond with partial charges (δ+ and δ−).

Question 30

What determines if a molecule has a permanent dipole?

Answer 30

If polar bonds are arranged asymmetrically, dipoles do not cancel, and the molecule has a permanent dipole. Symmetry may cancel polarities.

Question 31

What are the three main types of intermolecular forces?

Answer 31

Van der Waals (induced dipole-dipole), permanent dipole–dipole, and hydrogen bonding.

Question 32

What are van der Waals forces?

Answer 32

Weak, temporary attractions between molecules due to fluctuating electron distributions causing temporary dipoles.

Question 33

What are permanent dipole–dipole forces?

Answer 33

Attractions between molecules with permanent dipoles due to differences in electronegativity.

Question 34

What is hydrogen bonding?

Answer 34

A strong type of dipole–dipole attraction between a hydrogen atom bonded to N, O, or F and a lone pair on another N, O, or F atom.

Question 35

Why is hydrogen bonding stronger than van der Waals or dipole-dipole?

Answer 35

Because of the large difference in electronegativity and the small size of hydrogen, leading to strong attractions.

Question 36

How do intermolecular forces affect boiling points?

Answer 36

Stronger intermolecular forces increase boiling points because more energy is needed to separate the molecules.

Question 37

Why does ice float on water?

Answer 37

Hydrogen bonding forms an open lattice structure in ice, making it less dense than liquid water.

Question 38

Why does water have an anomalously high boiling point?

Answer 38

Strong hydrogen bonding between water molecules requires more energy to break compared to similar-sized molecules.