Question

The most abundant metal in the earth’s crust is:
A. Silver
B. Aluminium
C. Calcium
D. Gold

Answer 1

Hint: Think about the composition of the earth’s crust and what types of compounds are found there in abundance, also consider the rarity of the other substances to help you narrow down the options.

Complete answer:
We will look at the rarity and compounds of each of the following metals that are given in the options and then narrow down the metals that are found abundantly in the earth’s crust.
- Silver
We know that silver is a precious metal that is rarely found in the earth’s crust relative to the abundance of the other metals. It is found in its free, native form as $Ag$ since it is a somewhat noble metal and does not react easily with other elements. So, this cannot be the most abundant metal.
- Aluminium
This is the third most abundant element in the earth’s crust, the first two are oxygen and silicon. 8% of the earth’s crust is made up of aluminium by weight. Now, we know that oxygen is a non-metal and silicon is a metalloid and both of them are not present in the given options. It is present in the forms of alum or potassium aluminium sulphate $[KAl{{(S{{O}_{4}})}_{2}}\cdot 12{{H}_{2}}O]$, and aluminium oxide $(A{{l}_{2}}{{O}_{3}})$ and almost never in its free state since it is a reactive metal.
- Calcium
Calcium is the fifth most abundant element in the earth’s crust, it is found in the in the forms of gypsum $(CaS{{O}_{4}}\cdot 2{{H}_{2}}O)$, limestone $(CaC{{O}_{3}})$ and other compounds. 3.5% of the earth’s crust is made up of calcium by weight.
- Gold
We know that gold is another precious metal along with silver and it is even rarer than silver in terms of abundance. Gold is found in its natural free state since it is a relatively noble metal and does not react easily and form different compounds.

Note:
Remember that calcium is included in the group ‘alkaline earth metals’ in the periodic table. But this just means that it is found in the form of alkaline compounds in the earth crust and does not indicate its abundance in any way.