What is the atomic nucleus made of ? only neutrons electrons only protons nucleons

nucleons

Explanation:

The nucleons are the particles that constitue the nuclei of the atoms. Those are protons and neutrons.

They are not elementary particles (quarks are the elementary particles that form both protons and neutrons).

Protons are the particles that define the elements. Any different elements have different number of protons. H has one proton, He has 2 protons, Li has three protons, Na has 11 protons, U has 92 protons.

Protons are positively charged and the number of protons in any neutral atom is equal to the number of electrons (the electrons, which are elementary negatively charged particles, are around the nucleous).

Neutrons have not charge and are responsible for the stability of the nuclei. They are fundamental to avoid that the repulsion forces between the positively charged protons ends causing the collapse of the nuclei.

Carbon based or cells?