Question: Neutrinos… so they are a subatomic particle, but they aren’t one of the particles that make up atoms, is that right? How would you explain to a child, who has a basic understanding of protons, neutrons and electrons, what neutrinos are?
They don’t make up atoms, correct, though they are emitted in radioactive beta decay.
I would say that neutrinos are like electrons, but with the electric charge taken away. Because the charge has been taken away, neutrinos find it very hard to interact with other particles, as most of the interactions that we see around us are related to electric charge. Therefore, a typical neutrino will go through almost anything without even noticing: 65 billion neutrinos from the Sun go through your thumbnail every second, but you will never notice! They also have even less mass than an electron: an electron weights only 1/1800 as much as a proton, but the neutrino probably weighs only a millionth as much as an electron!
However, even though they are so small and so hard to detect, neutrinos are very important, because the nuclear reactions that allow the Sun to shine would not be able to happen without neutrinos.