Answer:
Nucleus, protons and neutrons
Step-by-step explanation:
An atom has a nucleus and and orbitals, the nucleus holds protons and neutrons while the orbitals hold electrons.
There are 3 types of particles, protons +, neutrons, o, and electrons -.
We could think of atoms like the Solar System. The sun is in the center and the orbits are where the planets go around.
An atom has a nucleus for the sun and orbitals as the orbits, electrons are the planets.
The nucleus hold protons and neutrons.
Which means the center of an atom is the nucleus and the nucleus holds protons and neutrons.