What particles are in the nucleus of an atom?

Protons and neutrons are present with in the nucleus of an atom.

Explanation:

Every atom consist of nucleus or a positive center. The protons and neutrons are present with in the nucleus while electrons are present out side the nucleus. All these three subatomic particles construct an atom. The number of protons or number of electrons are the atomic number of an atom while the number of protons and number of neutrons are the mass number of an atom. A neutral atom have equal number of protons and electrons. In other words we can say that negative and positive charges are equal in magnitude and cancel the each other.

Electron:

The electron is subatomic particle that revolve around outside the nucleus and has negligible mass. It has a negative charge.

Symbol = e-

Mass = 9.10938356*10-31 Kg

It was discovered by j. j. Thomson in 1897 during the study of cathode ray properties.

Neutron and proton:

The neutron and proton are present inside the nucleus. Proton has positive charge while neutron is electrically neutral. Proton is discovered by Rutherford while neutron is discovered by James Chadwick in 1932.

Symbol of proton = P+

Symbol of neutron = n0

Mass of proton=1.672623*10-27 Kg

Mass of neutron=1.674929*10-27 Kg