1. Chemistry: Inside the Atom Chapter 3 Part 2

2. How Atoms Differ Atoms differ in the number of protons they have. – Oxygen has 8 Protons, Fluorine 9 Protons, Gold 79 Protons – The number of protons gives the element its identity

3. Atomic Number & Mass Number Atomic Number - The Number of protons in the nucleus of an atom – The number of protons and electrons are the same in a neutral atom. Mass Number – is the number of neutrons plus protons – # of Neutrons = Mass Number – Atomic # – The number of Protons and Neutrons contribute to the mass of an atom

4. Isotopes Isotopes – atoms of the same elements with different numbers of neutrons – All isotopes of any element have the chemical properties of that element Carbon - 12Carbon – 14 Isotope Mass Number1214 Number of Protons66 Number of Neutrons68 Number of Electrons66 Atomic Number66

5. How Atoms Are Represented Chemical Symbol – a notation of 1 or 2 letters that represent an element – 1 st letter Capital – 2 nd Letter Lower Case – Example: Gold Au, Iron: Fe, Oxygen: O The symbol also represents the atoms – Ca = 1 atom of calcium – 4Al = 4 atoms of Aluminum – 6O = 6 atoms of oxygen