Dmitri Mendeleev -discovered set of patterns that applied to all elements

-1869 published 1st periodic table

-total of 63 elements discovered

-wrote properties of each on note cards (density, color)

-noticed pattern when he arranged them in order of increasing atomic mass

Atomic Mass

Periodic Table

-average mass of all isotopes of an element

-properties of elements repeat in each row of table

Henry Moseley

-1913, discovered how to measure protons = atomic number

-table rearranged by atomic number

Periods

Groups/Families

Element Squares

-horizontal rows-series of different

elements (like days in a week)

-18 vertical columns-elements with

similar characteristics

-includes:atomic numberchemical symbolnameatomic mass

Chemical Symbol

Average Atomic Mass

-one or two letters representing an element

-abbreviations of English and Latin names

-most elements consist of mix of isotopes

-determined from combined percentages of all isotopes

Metal

-characterized by physical properties

-shininess, malleability, ductility, conductivity

-some are magnetic: iron (Fe), nickel (Ni)

-most are solid at room temperature, except mercury (Hg) - liquid

Malleable

Ductile

Conductivity

• hammered/pounded into shapes

• -pulled out into wires

• -ability to transfer heat or electricity to another object

Reactivity

-chemical property

-ease at which an element reacts with other elements/compounds

-usually react by losing electrons

-↓ from highly reactive to less reactive as you move left to right across table

Corrosion

Alkali Metals

-wearing away of metal-due to chemical reaction

-group 1-loses one electron-extremely reactive-never found uncombined

in nature, only in compounds

Alkali Metals

-when pure: shiny and very soft (cuts with plastic knife)

-sodium (Na) and potassium (K) important for life*salt, foods

-lithium (Li)*batteries, medicines

Alkaline Earth Metals

-group 2-loses two electrons-fairly hard, gray-white-good conductors-very reactive-never found uncombined-magnesium (Mg)

plus aluminum = light weight material used for ladders, wheels, planes

-calcium (Ca)essential for bones, teethin milk, dairy, green veggies

Transition Metals

-groups 3-12-iron (Fe), copper (Cu),

silver (Ag)-most hard and shiny-all good conductors of

electricity-less reactive than groups

1 and 2

Metals in mixed groups

Lanthanides

-groups 13-15-not very reactive-aluminum (Al), tin

(Sn), lead (Pb)

-top row at bottom of table

-soft, malleable, shiny, high conductivity

-mixed to make alloys-many found together;

difficult to separate

Alloy

Actinides

-mixture of two or more metals

-below lanthanides-only actinium (Ac),

thorium (Th), protactinium (Pa), and uranium (U) occur naturally

*U used for energy in nuclear power plants

-all elements heavier than U created in labs

*nuclei very unstable*many only last a fraction

of a second after made

Synthetic Elements

Particle Accelerators

-higher than #92-synthesized when

nuclear particles are forced to crash into each other

-move atomic nuclei faster and faster

-when crash, enough energy to make a single nucleus

-heavier than 95

Nonmetal

-lacks most properties of metals-poor conductors-good insulators-dull and brittle-10 of 16 are gases at room temp-bromine (Br) only liquid at room temp-reactive with other elements; form

compounds easily-gain or share electrons-fluorine (F) most reactive element

Carbon Family

-group 14

-gain, lose, share 4 electrons

-only carbon (C) is nonmetal

-C found in all living thing

-many fuels contain C: coal, gasoline

Boron Family group 13

have 3 valence electrons

Boron (B) is the only metalloid, all other are metals

most common metal is aluminum (Al)

Nitrogen Family

Diatomic molecule

-group 15-two nonmetals:

nitrogen (N) and phosphorous (P)

-gain, share 3 electrons

-80% atmosphere is N gas (N2)

-consists of two atoms (N2, O2)

Nitrogen Family

-N is useful in fertilizer

-P more reactive than N

-P used to make matches (reacts with oxygen)

Oxygen Family

-group 16

-3 nonmetals: oxygen (O), sulfur (S), selenium (Se)

-gain, share 2 electrons

-O necessary for life (O2)

- is ozone (filters radiation from sun)

-O highly reactive (reacts with almost all other elements

-O most abundant element in crust

-S used to make rubber bands, tires

Halogen Family

-group 17

-fluorine (F), chlorine (Cl), bromine (Br), iodine (I), astatine (At

-salt forming

-gains, shares 1 electron

-very reactive

-dangerous to humans uncombined

-useful when combined (F prevents tooth decay, Cl used in table and rock salt)

Noble Gases -group 18

-un-reactive

• -don’t gain or share electrons

-Helium (He), Neon (Ne), Argon (Ar), Krypton (Kr), Xenon (Xe), Radon (Rn)

-exist in small amounts in atmosphere

-used in electric lights, (He) in balloons

Hydrogen

-above group 1

-simplest, smallest element

-1 proton, 1 electron

-makes up 90% of atoms, but only 1% of mass of crust, oceans, atmosphere

-most in form of water (H2O)

Metalloids

-characteristics of metals and nonmetals

-zig za

-all solid at room temp

-brittle, hard, somewhat reactive

-most common silicon (Si)

-Si makes up sand, which makes glass

-most useful prop is varying ability to conduct electricity

*depends on temp, light, impurities

Semiconductors

-conduct electricity under some conditions, but not others

-used for computer chips, transistors, lasers