Structure and Bonding

Question 1

Ionic bonds

Answer 1

Metals transfer electrons to a non-metal to achieve a full outer shell. There are strong electrostatic forces of attraction between oppositely charged ions

Question 2

Common ion formulas + charges

Answer 2

Ammonium - NH4+
Hydroxide - OH-
Carbonate - CO32-
Nitrate - NO3-
Sulfate - SO42-
Chloride - Cl-

Question 3

Ions in ionic bonds

Answer 3

Metals lost electrons to form cations (e.g. Li+)
Non-metals gain electrons to form anions (e.g. Cl-)

Question 4

Melting + boiling points of ionic structures

Answer 4

• Solids at room temperature
• Melting + boiling are state changes
• High melting + boiling points because ionic bonds have strong electrostatic forces of attraction between ions

Question 5

Electrical conductivity of ionic structures

Answer 5

• Conduct electricity only when molten to form a liquid or dissolved in water to form an aqueous solution
• Both processes make ions free to move and conduct electricity

Question 6

Covalent bonds

Answer 6

Strong electrostatic forces of attraction between the shared pair of electrons and nuclei of both atoms. It involves non-metals only.

Question 7

Simple covalent structures

Answer 7

H2O, water
O2, oxygen
HCl, hydrogen chloride
CH4, methane
NH3, ammonia
CO2, carbon dioxide

Question 8

Melting + boiling points of simple covalent structures

Answer 8

• Low melting and boiling points because the attractions between molecules are weak and easy to overcome. *Covalent bonds are NOT broken

Question 9

Electrical conductivity of simple covalent structures

Answer 9

• Simple covalent molecules have no free ions or electrons
• They cannot conduct electricity (insulators)

Question 10

Other properties of simple covalent structures

Answer 10

• Volatile (vaporises easily)
• Most are not soluble in water, but may dissolve in other solvents (e.g. cyclohexane)

Question 11

Giant covalent structures

Answer 11

A 3D structure of atoms joined by covalent bonds (e.g. diamond, graphite, fullerene)

Question 12

Giant covalent structure examples

Answer 12

• Graphite, diamond, and fullerene are all allotropes of carbon in solid form
• Carbon can form up to 4 covalent bonds

Question 13

Melting + boiling points of giant covalent structures

Answer 13

High melting + boiling points - large amounts of energy are needed to overcome their strong covalent bonds

Question 14

Electrical conductivity of giant covalent structures

Answer 14

• Most substances have no charged particles that are free to move, so most cannot conduct electricity
• Graphite is an exception

Question 15

Metallic bonding

Answer 15

• Metals form giant structures in which electrons in the outer shells of atoms can move
• The metallic bond is the strong electrostatic forces of attraction between metal ions (+) and delocalised electrons (-)

Question 16

Metallic elements/ions

Answer 16

• Na+, sodium
• K+ potassium
• Li+, lithium
• Ca2+, calcium
• Cu2+, copper (II)

Question 17

Melting + boiling points of metals

Answer 17

• High melting + boiling points (strong metallic bonds)
• Energy is needed to overcome the forces of attraction between the metal ions and delocalised electrons
• Metals form lattices, so there is a large number of electrostatic forces to be broken

Question 18

Electrical conductivity of metals

Answer 18

• Delocalised electrons can travel through the lattice structure, so an electric current can be formed. Therefore, metals can conduct electricity
• Metals IONS and NOT able to move (held in fixed positions)

Question 19

Why graphite is slippery

Answer 19

The forces between the layers in graphite are weak. This means that the layers can slide over each other.

Question 20

Giant ionic lattices

Answer 20

• No limit to the number of particles present
• Regular arrangement of ions
• Each ion is surrounded by ions with opposite charges
• high melting + boiling points because it takes a lot of energy to overcome strong electrostatic forces of attraction between oppositely charged ions

Question 21

Physical properties of metals

Answer 21

• High melting/boiling points - lots of electrostatic forces to be broken
• Good conductors of heat and electricity - delocalised electrons
• High density - atoms packed closely into a small space
• Malleable + ductile - atoms can roll over each other into new positions without breaking the metallic bond

Question 22

Why relative molecular mass causes melting + boiling points to increase

Answer 22

This is because larger molecules have more intermolecular forces between them. These forces, although weak, must be overcome if the substance is to boil.