2. Atoms & Bonding Ch. 4-5

3. Democritus - ancient Greek Universe made of small invisible units (atoma) “unable to be divided” J. Dalton (English, 1808) all atoms of an element are the same can form compounds

4. The Periodic Table originally organized by D. Mendeleev (Russian, 1869) by atomic mass originally organized by D. Mendeleev (Russian, 1869) by atomic mass H. Moseley (English, 1911) rearranged elements in order of increasing atomic number

5. Atom a central nucleus of protons & neutrons (like a clump of grapes) Electrons move around the nucleus in a cloud nucleus area where you might find an e -

6. protons, p + (positive charge) neutrons, n° (no charge) electrons, e - (negative charge)

7. A neutron walked into a restaurant and asked how much for a hamburger. The waiter replied, “For you, no charge." ATOMIC HUMOR

8. What does it all mean? p + = atomic number e - = p + (all elements on periodic table start neutral) Atomic mass = p + + n° n° = atomic mass - atomic number

9. Periods – rows; not much in common Groups/families – columns; share lots of properties & characteristics

10. Models explain how atoms behave Bohr Diagram shows p +, n°, e - shells (no element symbol) Electron Dot Diagram element symbol & valence e - e - on the outermost shell (from Bohr diagram) key to why atoms bond together

11. Nitrogen (___) Atomic #: ___ Atomic mass: ___ # of p + : ___ # of e - : ___ # of n°: ___

12. Sodium (___) Atomic #: ___ Atomic mass: ___ # of p + : ___ # of e - : ___ # of n°: ___

13. Chlorine (___) Atomic #: ___ Atomic mass: ___ # of p + : ___ # of e - : ___ # of n°: ___

14. Elements always want to have a full outer shell to be stable 8 e - make a full outer shell (only 2 e - on 1 st shell) So, e - will move around until the atom is stable What is the “MAGIC” number?

15. 17p + 18n° Na 1+ Cl 1- NaCl neutral compound! 11p + 12n° 11p + 11e - 17p + 17e - 10 XX 18

16. d. cation: positive ion formed when e - are LOST lose e -, so they have more positives (p + ) d. anion: negative ion formed when e - are GAINED gain e -, so they have more negatives (e - ) Becoming Ions

17. cation: name stays the same anion: drop the end, add “-ide” Ex. NaCl – _______________________ Ex. MgO – _______________________ Ex. CaF2 – _______________________ Naming Ionic Compounds