Question

What are the strong and weak forces in an atom?

Answer 1

The strong force holds nuclei together like glue, even though protons should repel.

The weak force causes flavour changes of quarks into other quarks, necessary for making larger elements.

Explanation:

The strong force is what sticks a nucleus together. Protons and protons shouldn't really be in the same place, because they have the same charge and repel each other. But the gluons - particles carrying the strong force, `g` bosons - stick them together to form the nucleus. The strong force doesn't vary with distance like gravity and electromagnetism, but only operates on tiny scales. It is still the strongest force, if only over these minute distances.

The weak force is the second weakest force (the actual weakest force being gravity), and, like the strong force, only acts over tiny distances. The weak force is carried through the `W^+`, `W^-` and `Z_0` bosons, which make quarks and leptons change into other quarks and leptons - called a flavour change. This is important because many types of radioactive decay involve quarks changing to other quarks, as does thermonuclear fusion in the sun to turn hydrogen into deuterium and helium for larger elements to be formed.