atoms

• What is an atom?

  An atom is the smallest particle of an element that can exist by itself and still have the same chemical properties of the element.
• What is an element?

  An element is a pure substance made from only one type of atom.
• What are the subatomic particles of an atom?

  Protons, neutrons, and electrons.
• What is the nucleus of an atom?

  The nucleus is a small central part of an atom made up of protons and neutrons.
• What are electron shells or energy levels?

  Electrons revolve around the nucleus in fixed orbitals called electron shells or energy levels.
• What is the mass number of an atom?

  The mass number is the sum of protons and neutrons in the nucleus.
• What is the atomic number?

  The atomic number is the number of protons in an atom.
• What is electronic configuration?

  Electronic configuration tells the number of electrons in each electronic shell of an atom.
• What are valence electrons?

  Valence electrons are the number of electrons in the last shell of an atom.