Chapter 10, Problem 1RQ

Why does helium fusion require a higher temperature than hydrogen fusion?

To determine

Why helium fusion requires a higher temperature than hydrogen fusion.

Answer to Problem 1RQ

The energy required for helium fusion is much higher than what is required for hydrogen fusion.

Explanation of Solution

Hydrogen has one proton in its nucleus whereas helium has two.

Protons are positively charged particles.

During fusion, two nuclei (or more) combine together to form a heavier nucleus.

Therefore, positive charges are brought together during fusion and bound into a single nucleus.

But, like charges repel. To hold them together, a large amount of energy is required.

Fusion of two hydrogen atoms involves binding two protons while helium fusion involves bringing together four protons.

Since the number of protons to be bound in helium fusion is more than that in hydrogen fusion, much more energy is required for this reaction to take place.

Therefore, helium fusion requires a higher temperature than hydrogen fusion.