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Atoms are tiny invisible particles of substances.
The surface of an atom is made of electrons (with negative charge). Its nucleus contains the same number of positive charges. So atoms are neutral.
Only the smallest particles of  NOBLE  GASES are atoms. In the other elements and in compounds  atoms combine by sharing or by exchanging electrons. (In the last case ions are formed).
Photo: Atoms with their bonding electrons can be visualized by table tennis ball with push-buttons
(white: hydrogen (1), red: oxygen (2), black: carbon (4).