An atom is:

An atom is:

• A. A large unit of matter
• B. A unit of energy
• C. The smallest unit of matter
• D. A type of molecule

Answer: (C)

An atom is the basic unit of matter that retains the properties of an element. It’s the smallest piece of an element that still behaves like that element in chemical reactions. Atoms have a dense nucleus containing protons and neutrons, with electrons circling around in regions called orbitals. The arrangement of these electrons, especially the outermost ones, governs how atoms bond with others to form molecules. So an atom isn’t a large unit of matter, it isn’t a unit of energy, and it isn’t a molecule—molecules are made when atoms bond together.

An atom is the basic unit of matter that retains the properties of an element. It’s the smallest piece of an element that still behaves like that element in chemical reactions. Atoms have a dense nucleus containing protons and neutrons, with electrons circling around in regions called orbitals. The arrangement of these electrons, especially the outermost ones, governs how atoms bond with others to form molecules. So an atom isn’t a large unit of matter, it isn’t a unit of energy, and it isn’t a molecule—molecules are made when atoms bond together.