Atoms are not solid masses but are rather composed of smaller particles. The basic building blocks of atoms are subatomic particles, namely protons, neutrons, and electrons.
Protons carry a positive electric charge, neutrons have no charge (they are neutral), and electrons carry a negative charge. Protons and neutrons are located within the central nucleus of an atom, while electrons orbit around the nucleus in specific energy levels or shells.
The nucleus of an atom is relatively small compared to the overall size of the atom, and it contains the protons and neutrons tightly packed together. The number of protons in the nucleus determines the atomic number and identifies the element, while the total number of protons and neutrons combined determines the atomic mass.
The electrons, which have a much smaller mass than protons and neutrons, occupy specific energy levels or shells around the nucleus. These energy levels are organized in a way that the innermost shell can hold up to 2 electrons, the second shell can hold up to 8 electrons, and so on. The electrons are responsible for the chemical behavior and interactions of atoms.
In summary, atoms are composed of protons and neutrons in the nucleus, with electrons orbiting around the nucleus. They are not solid masses but rather dynamic systems of subatomic particles.