2. 1. Atom – smallest part. 2. Prot. = electrons (balanced) 3. Most of volume is space between nucleus & electrons 4. - w/lowest energy electron closest to nucleus, those w/ most energy far away 5. amu (atomic mass unit) = mass of atom, 1 amu = mass of proton or nuetron.

3. Elements can be identified by # of protons (atomic #) isotope = same # of + and -, but different # of nuetrons Carbon atomic # is 6, has isotopes C-13, and C-14 – react the same Mass # is average of sum of isotope.

4. Models are used to show something we can’t see easily....like an atom

5. Mendeleev looked at M.P, B.P, density, mass, color and made cards which he put in an organized table. Noticed a pattern. Periods showed a pattern from L (reactive) to R (not reactive). Current table – arranged by atomic number

6. Each element has one square showing: atomic number (number of +), atomic mass (average mass of isotopes), chemical symbol (letter – usually from Latin word) Properties of element change when going from L – R in a predictable way. 7 periods. The Lanth. and Actinides are part of the 7 th period. (horizontal rows showing reactivity) 18 groups – shows free electrons in the outer shell. (same)

7. Metals Physical properties include: Shiny Malleable – rolled into a sheet Ductility – pulled out into long wire Conductivity – transfer heat or electricity Some metals react by losing an electron. Some are very reactive in water so stored in oil – closed container.

8. Sodium (Group 1) in water/oil

9. Alkali Metals – Group 1 Lose 1 electron Very reactive Never uncombined in nature (compounds) Shiny & soft – cut with knife

10. Alkaline Metals Hard, grayish white React by losing 2 electrons Good conductors of electricity Not as reactive as Group 1 Never found as uncombined elements in nature Magnesium and calcium

11. Transition Metals – Groups 3 - 12 Iron, copper, nickel, gold, Hard and shiny Good conductors – form colorful compounds Not very reactive – good for jewelry! We use these a lot!

12. Metals in Mixed Groups Some of the elements in Groups 13 – 15 Aluminum, tin, lead Not reactive at all compared to the left side Protect from corrosion of other metals. (Tin is used in thin layer in cans)

13. Lanthanides (a) Actinides (b) The two rows at the bottom of Periodic table. (a) soft, malleable, shiny, conductor. Used with other metals (alloy) Found usually with another - a mixture – in nature. (b) Thorium and uranium found naturally. All others are synthetic – man made. Bombard nuclei in a particle accelerator. They sometimes combine when they collide. 3 letters (uuu) are given til they are formally named.

14. Non-metals – lack the properties of a metal, (poor conductors, but reactive with other elements. (so they form compounds – except group 18) 10 of 16 are gases at room temp Carbon, iodine, sulfur are solid – dull/brittle Bromine - liquid at room temp Group 18 all non-metals, Groups 14-17 is a mix of non-metals and “other” Carbon family – each element has atoms that can gain, lose, or share 4 electrons. Carbon found in ALL living things

15. Nitrogen and Oxygen Families Group 15 – 2 non-metals Gain or share 3 electrons Nitrogen – diatomic molecule – consists of 2 atoms. Not reactive, bacterial use N2 to form compounds – nitrogen fixation Phosphorus – much more reactive, so found in nature in compounds – found in matches since it reacts with oxygen in air. Oxygen - Group 16 – 3 non- metals Gain or share two electrons Oxygen is diatomic Triatomic – is ozone Very reactive with almost every other element. Most abundant in earth’s crust, and 2 nd most in air.

16. Halogens Group 17 Means salt-forming All but astatine are non-metals Typically gains or shares 1 electron. Very reactive – uncombined elements – very dangerous Many uses when combined. Noble Gases Group 18 Do not usually gain, share or lose an electron (unreactive) All the gases exist in our atmosph. Helium – discovered late. Hydrogen- not a noble gas but by itself in upper left corner. One proton, one electron, simplest and smallest, different from all other elements so not in any group.

17. Metalloids Between metals and nonmetals. have characteristics of both Silicon – common Can vary their ability to conduct electricity, making good semi- conductors (conduct electricity under some conditions)