what is atom

An atom is the basic unit of matter and the smallest particle that retains the chemical properties of an element. Atoms are made up of a central nucleus, which contains positively charged protons and uncharged neutrons, surrounded by negatively charged electrons that orbit the nucleus in shells. The number of protons in an atom's nucleus determines what element it is. For example, an atom with one proton is hydrogen, while an atom with six protons is carbon. Atoms can have varying numbers of neutrons, which gives rise to isotopes of the same element, but the number of electrons in an atom is always the same as the number of protons, giving the atom a net electrical charge of zero. Atoms are extremely small and cannot be seen with the eye. The study of atoms and their properties is the basis of the field of chemistry and plays a fundamental role in many other scientific disciplines, including physics, biology, and materials science