ATOMS

ATOMS

1. have a small central nucleus

   • contains protons and neutrons
     • surrounded by electrons
       • relative charge of electrons is -1
     • relative charge of neutrons is 0
     • relative charge of protons is +1

2. there are an equal amount of electrons in an atom to protons and neutrons

   • atoms have no overall electrical charge

3. all atoms of a particular element have the same amount of protons

   • atoms of different elements have different amounts of protons

4. protons in an atom are represented by the atomic number

   • atomic number is on the bottom when an element is shown on the periodic table

5. a mass number is the sum of protons AND neutrons in an atom

   • mass number is on the top when an element is shown on the periodic table

6. electrons occupy particular energy levels

   • each electron in an atom is at a particular energy level (in a particular shell)
     • the electrons in an atom occupy the lowest energy levels (inner available shells)
       • there can only be a maximum of 2electrons in the inner shell
         • maximum of 8 electrons in the 2nd and 3rd shells
           • electrons on an atom diagram are shown as dots
             • example: atomic number 13
               • 2 electrons in the circle closest to the nucleus
               • 8 electrons in the next shell
               • 3 electrons in the last shell
             • shells are shown as circles in a diagram of an atom