1. Atomic Structure  Atomic Number = # Protons  Atomic Mass = Protons + Neutrons (also called mass number)  If atom is neutral (a charge of zero), electrons = Protons

2. Atomic Structure  Nucleus is full of protons & neutrons.  Nucleus contains nearly all the mass of the atom  Electrons are very small relative to the protons and neutrons.  Electrons have a negative charge -  Protons have a positive charge +  Neutrons have no charge. 0

3. Reading the Periodic Table Atomic Number 3 Li 6.941 Lithium Element Symbol Element Name Atomic Mass # p roton + # e lectron - (in a neutral atom) # p + + # n 0 # n 0 = Atomic Mass - #p +

4. Mass Number/ Atomic Mass Mass # = protons + + neutons 0 Element p+p+ n0n0 e-e- Mass # Oxygen8 3342 15 2964 Neon 10 8816 Arsenic 3375 Phosphorus 153116 35 29Copper 101020

5. Practice Sheet

6. Atomic Structure  Where are the electrons?  What are electron shells?  How many electrons per shell?

7. Electrons are in shells that circles the nucleus at light speed.

8. Electron Shells The letter n, represents the electron shell. Number of electrons that can fit in a shell: 2n 2 Electron Shell 1 can hold: 2e - Electron Shell 2 can hold: 8e - Electron Shell 3 can hold: 18e - Electron Shell 4 can hold: 32e -

9. Energy Level 1 can hold: 2e - Energy Level 2 can hold: 8e - Energy Level 3 can hold: 18e - Energy Level 4 can hold: 32e - Things to remember: The element’s period # = the # of electron shells There can only be 2 e - in the first energy level All atoms want to have 8 electrons on their outer shells

11. Valence Electrons  Valence electrons  Valence electrons – Electrons on highest energy level / highest electron shell.

12. COOL FACT about atoms!  Most of the volume (space) of an atom is made up of electrons  Electrons have very little mass and take up very little space  SO, atoms are mainly empty space  We are made of atoms SO we are empty mainly made up of Empty Space

13. Sulfur Nucleus # Neutrons: # Protons: # Electrons:

14. Chlorine Nucleus # Neutrons: # Protons: # Electrons: