The atom is the fundamental particle of matter that consists of protons, neutrons and electrons. The protons and neutrons are located in the central nucleus, while electrons surround the nucleus. The atom cannot be split by any chemical means.
The protons are positively charged, while electrons are negatively charged. If the charges of protons and electrons are equal but opposite, the atoms are neutral. If the number of electrons is larger than the number of protons, the atom is called anion. If the number of electrons is smaller than the number of protons, the atom is called cation.
An element can have different number of neutrons, but the same number of protons, each combination of neutrons and protons defining an isotope of the element.
An atom is the basic building block of matter. It is composed of a nucleus with neutrons (neutral charge) and protons (positive charge). There is also a cloud of electrons (negative charge) that surround the nucleus. If the number of protons and electrons do not equal, the atom is an ion. You can differentiate atoms by the number of protons it has, which is the same thing as an element's atomic number. Atoms are bonded to form molecules and form larger substances.
Atoms are what make up matter. The smallest amount of matter you can break it up is an atom. A microscopic particle filled with neutrons, electrons, and protons.