The center of an atom is called the nucleus. It is a small, dense region located at the core of the atom. The nucleus is composed of protons and neutrons, which are collectively known as nucleons. Protons carry a positive electric charge, while neutrons are electrically neutral.
The nucleus of an atom contains nearly all of its mass but occupies only a tiny fraction of its volume. The protons in the nucleus are positively charged, and they are held together by the strong nuclear force, which overcomes the electrostatic repulsion between positively charged particles. Neutrons, as their name suggests, do not carry an electric charge and contribute to the mass and stability of the nucleus without directly affecting the atom's electrical properties.
Surrounding the nucleus, there is another region called the electron cloud or electron shell. The electrons, which are negatively charged, occupy various energy levels or orbitals within the electron cloud. Electrons are much smaller and lighter compared to the protons and neutrons, and they contribute very little to the overall mass of the atom.
In summary, the center of an atom is the nucleus, which contains protons and neutrons, while the electrons are found in the electron cloud surrounding the nucleus.