Atom

Atoms are the fundamental building blocks of all matter. They consist of a dense nucleus made up of positively charged protons and neutral neutrons, surrounded by a cloud of negatively charged electrons. The number of protons in an atom's nucleus determines its chemical identity, while the number of neutrons can vary, giving rise to different isotopes of the same element. The electrons are arranged in orbitals around the nucleus, and their interactions govern an atom's chemical properties.