A nucleus consisting of protons and neutrons in the center, and electrons orbiting a nucleus.
A neutron is an elementary uncharged particle. The electric charge is 0 e, the mass is 1 a. ie, the neutron was discovered in 1932 by Chadwick in the course of a nuclear reaction between beryllium and helium atoms. Neutron is part of the atomic nucleus
Proton is an elementary positive particle. The electric charge is +1 e, the mass is 1 a. e. m. Opened in 1919 by Rutherford. It is part of the atomic nucleus together with the neutron, it is the nucleus of a hydrogen atom.
An electron is an elementary negative particle. The electric charge is -1 e (equal in magnitude to the charge of the proton), the mass is 0,00054 a. EM, therefore, for simplicity of calculations it is believed that the electron has no mass. It was discovered in 1897 by Thomson when studying the behavior of cathode rays (electrons) in a magnetic and electric field. Electrons are not part of the nucleus, but are outside, moving along special trajectories, but more on that later.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.