What are the roles of protons, neutrons, and electrons in an atom?

Protons determine the atomic number, neutrons contribute to atomic mass, and electrons dictate the atom's chemical behaviour.

Protons, neutrons, and electrons are the three main subatomic particles that make up an atom. Each of these particles plays a unique role in determining the properties of an atom.

Protons are positively charged particles found in the nucleus of an atom. The number of protons in an atom, also known as the atomic number, identifies the element. For example, hydrogen has one proton, helium has two, and so on. The number of protons in an atom remains constant, barring nuclear reactions. This means that changing the number of protons in an atom changes the type of element it is.

Neutrons are neutral particles, also located in the nucleus. They contribute significantly to the atomic mass but do not affect the atomic number. The number of neutrons in an atom can vary, leading to the formation of isotopes. Isotopes are atoms of the same element (same number of protons) but with different numbers of neutrons. This variation in neutron number can affect the stability of the atom, with some isotopes being radioactive.

Electrons are negatively charged particles that orbit the nucleus in energy levels, or shells. The arrangement and behaviour of these electrons primarily determine the atom's chemical properties. Electrons are involved in bonding, as they can be shared, lost, or gained during chemical reactions. The outermost shell, or valence shell, is particularly important in determining how an atom interacts with others. Atoms strive to have a full valence shell, often leading to the formation of bonds with other atoms.

In summary, protons define the identity of an atom, neutrons contribute to its mass and stability, and electrons dictate its chemical behaviour. Understanding these roles is fundamental to the study of atomic structure and chemistry as a whole.