The picture shows a close-up of one carbon atom. A hydrogen atom has one proton as the nucleus and one electron in the region outside the nucleus. The electron and proton are attracted to each other.

A is the mass number (the sum of the protons and neutrons) Z is the atomic number (the number of protons) X is the chemical symbol of the element Note: the number of neutrons in the nucleus can be ...

The mass of an electron is very small ... Hence atomic number = 18 Number of protons + neutrons = 18 + 22 = 40. Hence mass number = 40The chemical symbol for argon with its mass number and atomic ...

In 1932, another British physicist, James Chadwick, discovered the neutron, another particle located within the nucleus. With the electron, proton, and neutron, scientists thought they had found ...

He called it a neutron, and imagined it as a paired proton and electron. There was no evidence for any of these ideas. Chadwick kept the problem in the back of his mind while working on other things.