An atom is the basic unit of matter. The atom is the basic building block of an element, and cannot be broken down further using any chemical means. An atom is made up of three particles: protons, neutrons and electrons.
The three particles of an atom carry different electrical charges. Protons carry a positive charge, electrons carry a negative charge, and neutrons have no electrical charge. Matter is anything that has mass and occupies space. All physical objects consist of matter in the form of atoms. Matter can exist as solid, liquid, gas or plasma. Some substances can transition between different states of matter depending on the amount of heat absorbed by the material.