Question

Although He is the second most abundant element in the universe, it is very rare on earth. Why?

Short answer

Helium is abundant in the universe as it was a by-product of the big bang. It is produced when a hydrogen fusion of the stars occurs.

Step-by-step solution

Define Elements

An element is a pure material made up entirely of atoms with the same number of protons in their nuclei.

Explanation of why helium is abundant.

Helium is very rare on earth, even though it is the second most abundant element in the universe.

Analyzing the explanation below as:

Helium exists on earth at a volume of 5.2 parts per million which exists freely in the atmosphere. Helium is said to be rare as in order to generate helium, there must be a radioactive decay of the elements that are highly radioactive such as thorium and uranium, underneath the deepest part of the earth's surface.

As helium production occurs from natural radioactive decay, we can never artificially produce it as it is relatively nonrenewable. This is the reason why helium is rare on earth.

Therefore, helium was abundant in the universe before it was a by-product of the big bang. Also, it is produced when a hydrogen fusion on the stars occurs.