Review: Element matter composed of one type of atom. Chemical symbols one or two letter abbreviations for elements, either one capital letter or two letters, first capital, second lower case

Atomic Components: Atom smallest piece of matter that retains the element’s properties, composed of particles called protons, neutrons and electrons

Nucleus center of atom, positively charged, containing protons and neutrons, contains most of the mass of an atom

Proton particles with a charge of +1, (mass of 1 amu) Neutron neutrally charged particles (mass of 1 amu)

Electron cloud area around the nucleus where electrons are most likely to be found Electrons particles with a charge of -1 (mass of 1/1,836 amu)

How to identify elements: Atomic number is the number of protons in an atom, it identifies the element A neutral atom has same number of protons and electrons

Isotopes Average atomic mass – the average of the mass numbers of all the same kind of atoms

Mass number – the most stable isotope, the amount of protons and neutrons in an atom (round the atomic mass) PROTONS + NEUTRONS = MASS NUMBER MASS NUMBER - PROTONS = NEUTRONS

Isotope- atoms of the same element with different numbers of neutrons Examples: Carbon-14 Potassium-40

Energy Levels and Bohr Models Energy Levels – named 1-7 in rows down the left hand side of the periodic table.

Row 1- holds 2 electrons max Row 2- holds 8 electrons max Row 3- holds 18 electrons max

Octet Rule- Outer energy level will up to 8 electrons (except which 2 elements?) Valence Electrons- Outermost energy level electrons, participate in chemical reactions

Periodic Table (3 main divisions) 1st Periodic Table 1869, Mendeleev arranged 63 known elements by mass and chemical properties. Modern tables are arranged by atomic number and properties.

Periods- 7 rows down left side, also corresponds with number of energy levels. Groups- a.k.a. families, 18 columns, have similar chemical properties because of valence electrons.

1 Metals- left side of stair step- most shiny and good conductors, tend to lose electrons in reactions

Alkali Metals (group 1)- highly reactive, lose 1 electron, shiny, soft Alkaline Earth Metals (group 2)- hard, grey- white, good electricity conductor, lose 2 electrons Transition Metals(groups 3-12)- hard and shiny, good conductors, less reactive than groups 1 and 2, ductile, malleable

2- Nonmetals- to the right of stair step, dull, brittle, poor conductors 10/16 are gasses, gain or share electrons in reactions

Carbon family (group 14)- can gain, lose or share 4 electrons, carbon is the element of life. Nitrogen family (group 15)- gain or share 3 electrons Oxygen family (group 16)- gain or share 2 electrons Halogen “salt forming” family (group 17)- gain or share 1 electron, very reactive, Fluorine is the most reactive non-metal, Noble gases (group 18) unreactive gases

3 Metaloids- bordering the stair step “semiconductors”, soft, brittle, solid, somewhat reactive