How many quarks are there in a neutron?
Okay, so to answer this relatively short question, we need to recall that both protons and neutrons, the two kinds of particle found in the nuclei of atoms, are made up of even smaller particles known as quarks, specifically two different kinds of quark. One is the up quark and the other is the down quark. Now, thinking about the electric charges on all of these particles, we can recall that a proton has a relative charge of positive one or, in other words, it’s a positively charged particle, whereas the neutron is neutral. It has a zero charge. And as well as this, the up quark has a relative charge of positive two-thirds. And the down quark has a relative charge of negative one-third.
Now focusing on the neutron specifically, because that’s what we’ve been asked to talk about in the question, we can call that a neutron is made up of one up quark and two down quarks because this way the total charge on the neutron is positive two-thirds from the one up quark minus one-third minus one-third. And so positive two-thirds minus one-third minus one-third ends up being an overall charge of zero. And so at this point, we can see that there are three quarks in a neutron, one up quark and two down quarks specifically. So we found the answer to our question.