Physics · nuclei · NEET
No. All electrons stay outside the nucleus. Early scientists thought the nucleus had electrons, but quantum theory ruled this out. The nucleus contains only protons and neutrons. Electrons move in the space around the nucleus.
Nucleon is the common name for the two particles inside the nucleus: the proton and the neutron. If a nucleus has Z protons and N neutrons, the total number of nucleons is A = Z + N. So the mass number A is just the count of nucleons.
Protons carry positive charge (+e each) and neutrons carry no charge. So the total charge of a nucleus with Z protons is +Ze. Since a full atom is neutral, the Z electrons outside carry equal negative charge -Ze, and they cancel out.
A proton has charge +e (one unit of positive charge) and mass about 1.00727 u. A neutron has zero charge and a slightly larger mass, about 1.00866 u. Both have nearly the same mass, but only the proton is charged. The number of protons (Z) decides which element it is.
Number of protons = atomic number Z. Number of neutrons = N = A - Z, where A is the mass number. For example, carbon-14 has Z = 6, A = 14, so protons = 6 and neutrons = 14 - 6 = 8.
The nucleus is the small, heavy centre of an atom. It holds nearly all the mass of the atom and carries positive charge. It is made of protons and neutrons.
Protons (positive charge) and neutrons (no charge). Together they are called nucleons.
A proton has mass about 1.00727 u (1.67262 x 10^-27 kg). A neutron has mass about 1.00866 u. They are almost equal, and both are about 1836 times heavier than an electron.
James Chadwick discovered the neutron in 1932. He fired alpha particles at beryllium and detected a neutral radiation that turned out to be the neutron.
Yes. Protons and neutrons are far heavier than electrons, so almost the entire mass of an atom sits in the nucleus, even though the nucleus is extremely small.
