1. Structure of An Atom Notes

4. PROTONS positive ( p+ ) Neutrons neutral ( n ° ) NUCLEUS e- e- e- e- e- e- e- e- e- Electron cloud ELECTRONS negative ( e- )

6. e- e- 2 8 18 Energy Levels NUCLEUS Energy Levels e- e- e- e- e- e- e- e-

7. 2 6 Example: Oxygen = 8 e- NUCLEUS e- e- Energy Levels e- e- e- e- e- e-

9. O Atomic Number Atomic Weight then if you ROUND You will get the… Mass Number = the sum of p+ and n ° Number of Neutrons = Mass # - Atomic # 8 15.9994 = + MASS NUMBER Number of p+ Number of n °

10. O So, why is this a decimal? It is an average of all the isotopes! What’s an isotope? 8 15.9994

11. The Nuclei of 3 isotopes of H+ PROTIUM DEUTERIUM TRITIUM + + + 1 PROTON 1 PROTON 1 NEUTRON 1 PROTON 2 NEUTRONS Atoms that have the same # of p+ but different # of n ° Definition

13. Atoms come together when the result is more ________ than the individual atoms stable e- e- 2 8 18 If filled to capacity then it is STABLE NUCLEUS e- e- e- e- e- e- e- e-

15. Method One: sharing electrons Example: Hydrogen unstable sharing electrons is called "covalent bonding" H e- H H e- e-

16. H H O stable & happy! H20 = water Examples of Molecules with Covalent Bonding: sugars, fats, proteins, & water

19. Na Cl Na Cl 11 e- 11 p+ 17 e- 17 p+ + unstable unstable

20. Na Cl ionic bond Ionic bond = attractive force between 2 ions of opposite charge stable