1.5 - Solid Structures

Question 1

Describe ionic structures and 3 reasons why their structure is optimal.

Answer 1

Made up of oppositely charged ions packed together
- maximises the attraction between ions
- minimises repulsion
- ensures maximum bond energy

Question 2

Describe the structure of ionic sodium chloride.

Answer 2

In NaCl, each cation is surrounded by 6 anions and vice versa.
Large cube structure, alternating na and cl.

Question 3

Describe the structure of ionic caesium chloride.

Answer 3

In CsCl, the number surrounding each is 8. This is because the Cs+ cation is larger than that of Na+, so has more room to accommodate a greater number of anions.
Small singular cube.

Question 4

What is the crystal coordination number for NaCl and CsCl?

Answer 4

NaCl - 6:6
CsCl - 8:8

Question 5

How many bonds can diamond and graphite make?

Answer 5

Up to 4 carbon bonds.

Question 6

What is the structure of diamond?

Answer 6

The carbon bonds strongly in a tetrahedral formation to form a giant 3D structure.

Question 7

What is the formation of graphite?

Answer 7

Only 3 bonds are made by each carbon atom, making hexagonal layers (monolayers) that are held together by weak forces.

Question 8

What is the structure of iodine?

Answer 8

Each molecule and layer is held together by weak intermolecular forces. The covalent bond between the 2 iodine atoms is very strong.
Picture cuboid, with iodine pair at every corner and middle of each face.

Question 9

What is the structure of ice?

Answer 9

Hydrogen bonds hold together the water molecules in a large tetrahedral structure. The strong bonding in the water molecule are polar convalent.

Question 10

What is metallic bonding?

Answer 10

The metal atoms become cations and squeeze out their electrons so that they are delocalised and form an electron sea around the metal ions. The interaction between the 2 holds them together in uniform shape.
Sandwich shape.

Question 11

What are the physical properties of ionic solids?

Answer 11

• hard, brittle and high melting points due to strong ionic bonds
• don’t conduct electricity when solid, but when molten they do due to free roaming electrons
• some are soluable in water, it takes alot of energy to break the ionic bonds though so it has to be energetically favorable.

Question 12

What are the physical properties of giant covalent solids?

Answer 12

• high melting points, insoluable in water
• diamond very hard structure as carbon is bonded with 4 others
• graphite is softer, useful as lubricant as layers slide
• graphite conducts electricity due to spare electron
• iodine is soft due to weak van de Waals forces

Question 13

What are the physical properties of metals?

Answer 13

• they conduct electricity and heat due to electron delocalisation, electrical conductivity increases with the number of delocalised electrons per atom
• hardness of metals depends on the number of delocalised electrons, the more electrons the harder it is.