1. ATOM NEUTRONS Charge: none Mass: 1 amu Location: nucleus ELECTRONS Charge: negative Mass: zero Location: electron cloud PROTONS Charge: positive Mass: 1 amu Location: nucleus NUCLEUS is the small, positively charged Center of the atom. It has most of the atom’s mass.

2. The mass of an atom is so small, scientist made a new SI unit, atomic mass unit (amu). In an atom, the numbers of protons and electrons are the same, so their charges cancel out. An atom has no overall electric charge, it is neutral. How can you tell which elements different atoms represent? The key is the number of protons. The number of protons in the nucleus of an atom is the atomic number of that atom.

3. The mass number is the total number of protons and neutrons in an atom. Subtract the atomic number from the atomic mass to find out the number of neutrons. Locate Fluorine on the periodic table. Mass: Atomic Number Protons: Electrons: Neutrons: 19 9 9 9 10 Mass Number (19) -Atomic Number (9) Neutrons (10)

4. Look at the Periodic Table, locate the following elements using their atomic number: carbon, potassium, gold. How many protons does Carbon have? How many electrons does Potassium have? How many neutrons does Gold have? 6 19 118