1. Breakthroughs in Organizing Elements Odling: elements can be organized into 13 groups based on physical & chemical properties Pretty close to modern groups GroupElements 1F, Cl, Br, I 2O, S, Se, Te 3N, P, As, Sb, Bi 4B, Si, Ti, Sn 5Li, Na, K 6Ca, Sr, Ba 7Mg, Zn, Cd 8Cr, Mn, Co, Fe, Ni, Cu 9Hg, Pb, Ag 10Pd, Pt, Au

2. Breakthroughs in Organizing Elements Newlands: assigned H a mass of 1 and ordered elements by relative mass Every 8 th element shared common properties – Noble gases weren’t discovered yet He called it the “law of octaves”

3. Dmitri Mendeleev Not to be confused with Dmitri Medvedev (Putin’s Prime Minister) Organized periodic table using mass & properties Accurately predicted undiscovered elements and even their properties!

5. The Modern Periodic Table

6. Key Terms Period: a row on the periodic table Group/family: a column Metals: left of the staircase Nonmetals: right of the staircase Semiconductors (metalloids): near staircase Atomic mass: weighted average of all isotopes Atomic number: number of protons

7. Key Groups & Oxidation States Oxidation state: the charge an ion of a certain element wants to obtain when forming bonds Group 1: alkali metals (+1) Group 2: alkaline earth metals (+2) Groups 3-12: transition (d-block) metals Group 16: chalcogens (-2) Group 17: halogens (-1) Group 18: noble gases (0) Groups 1,2, 13-18: main group elements

8. Charges of Ions Why are they the way they are? Remember the octet rule? Full valence shells are the most stable Shells hold max of 2, 8, 8, 18, 18, 32 Look at the periods of the periodic table…notice anything?

9. Charges of Ions Atoms of elements try to gain or lose electrons to achieve full valence On the right we have 2 valence e - Easier to lose 2 than gain 6 for full octet Lose 2 e -, charge would be 2+ 12 e - when neutral, so the ion would be Mg 2+

10. Bohr Diagrams Write the number of protons and neutrons (look at atomic mass) inside Draw circles to represent shells of the atom Add electrons as needed

11. Practice Draw the Bohr diagrams of the following: S 2-, Ne, Al 3+, K +, Ca