An atom is composed of three main types of subatomic particles:
- Protons : Positively charged particles located in the nucleus (the atom's central core). The number of protons defines the element and its atomic number. For example, an atom with 11 protons is sodium, while one with 29 protons is copper
- Neutrons : Electrically neutral particles also found in the nucleus. Neutrons contribute to the atom's mass and determine isotopes of an element, which are atoms with the same number of protons but different numbers of neutrons
- Electrons : Negatively charged particles that orbit the nucleus in a cloud or swarm. Electrons balance the positive charge of protons in a neutral atom and participate in chemical bonding
The nucleus, containing protons and neutrons, holds more than 99.9% of the atom's mass but occupies an extremely small volume compared to the overall size of the atom, which is mostly empty space where electrons move
. In summary, an atom consists of a dense nucleus of protons and neutrons surrounded by a cloud of electrons bound by electromagnetic forces
