Bonding and periodicity

Question 1

What is an ionic bond?

Answer 1

Two ions stuck together by electrostatic attraction. Metal + Non-metal. Metal loses electrons to become positive. Non-metal gains electrons to become negative. e.g. NaCl, CaCl2, MgO

Question 2

Ionic Compounds

Answer 2

• M + NM.
• Consist of giant ionic lattices, held together in a regular arrangement by strong, electrostatic forces of attraction between the oppositely charged positive metal ions, and the negative non-metal ions.
• High mpt/bpt
• Conduct electricity when melted or dissolved.

Question 3

Covalent bonding

Answer 3

NM + NM. Non-metals share electrons to get a FOS. e.g. HCl, Methane: CH4, CO2, CO.

Question 4

What happens to the electrons in a covalent bond?

Answer 4

They are shared between the atoms.

Question 5

Properties of the macromolecule, graphite

Answer 5

• Weak bonds between layers mean they can slide over each other.
• The delocalised fourth outer electron is free, so an electric current can flow.
• Layers are far apart in comparison to the length of the covalent bonds, giving graphite a low density which is useful for making strong, lightweight sports equipment.
• Very high melting point (sublimes at over 3900 K) due to the strong covalent bonds in the hexagonal sheets.
• Insoluble as the covalent bonds are too difficult to break.

Question 6

Properties of the macromolecule, diamond

Answer 6

• High melting point
• Extremely hard
• Good thermal conductor as vibrations travel easily through the stiff lattice
• Can’t conduct electricity
• Will not dissolve in any solvent

Question 7

What is dative covalent bonding?

Answer 7

Both electrons come from one atom, instead of one from each.

Question 8

Covalent bonding: simple molecular

Answer 8

Very strong covalent bonds between molecules. Weak intermolecular forces. Low mpt/bpt; gases, or liquids at room temperature, and don’t conduct electricity as they have no ions, or free electrons.

Question 9

Covalent substance: Giant covalent/macromolecules

Answer 9

Every atom is bonded to multiple atoms by very strong covalent bonds. Very high mpt/bpt, solid at room temperature, don’t conduct electricity (except graphite) even when molten as no free ions/electrons. e.g. diamond, silicon dioxide (silica), graphite.

Question 10

Silicon dioxide/silica (Giant covalent/macromolecule)

Answer 10

Sand (each grain is one giant structure of silicon, and oxygen). Each carbon has 4 bonds. very high mpt/bpt, doesn’t conduct electricity at all.

Question 11

Metallic structure

Answer 11

M + M. Metals are a giant structure that consist of a regualr arrangement of positive metal ions in a ‘sea’ of free/delocalised negative electrons. They are held together by the strong electrostatic forces of attraction between the positive ions, and negative electrons. They are also positioned in layers. This means that they are malleable/ductile as the layers can slide over each other.

Question 12

Alloy

Answer 12

A material that is composed of at least two metals (or a metal, and a non-metal). Alloys (like steel) are harder than normal metals as the layers of ions are locked in place, and cannot slide over each other. This is because alloys are made of different sized atoms.