Aerospace components, such as structural brackets for communication satellites, are manufactured from advanced lightweight alloys to ensure they are both exceptionally strong and low in density. One such bracket has a total mass of 3.20 kg3.20\text{ kg}3.20 kg.
The table below shows the mass of each element present in this bracket:
| Element | Mass in kg\text{kg}kg |
|---|---|
| Aluminium | 2.848 |
| Copper | 0.288 |
| Lithium | 0.064 |
The diagram below contrasts the atomic arrangement in a pure metal with that of an alloy:
a.[2]
Calculate the percentage by mass of aluminium in this bracket.
b.[4]
Explain, with reference to their atomic structures, why an aluminium alloy is used instead of pure aluminium to manufacture aerospace structural components.