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

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 .

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

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  1. 1. Atom – smallest part.2. Prot. = electrons (balanced)3. Most of volume is space between nucleus & electrons4. - w/lowest energy electron closest to nucleus, those w/ most energy far away5. amu (atomic mass unit) = mass of atom, 1 amu = mass of proton or nuetron.

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

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

  4. 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

  5. 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 7th period. (horizontal rows showing reactivity) • 18 groups – shows free electrons in the outer shell. (same)

  6. MetalsPhysical 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.

  7. Sodium (Group 1) in water/oil

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

  9. 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

  10. 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!

  11. 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)

  12. 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.

  13. 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

  14. 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 2nd most in air.

  15. Halogens 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. • 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.

  16. 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)

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