The Periodic Table Introduction to the Periodic Table Representative Elements Transition Elements

Development of the Periodic Table In 1830 there were 55 elements isolated and named Dmitri Mendeleev’s (1869) developed a Table of Elements by ordering them in increasing atomic mass Elements with similar properties fell into groups Mendeleev left 3 spaces for elements yet to be discovered and spurred interest in finding those elements (he also predicted their properties (15 years later all were identified)

Moseley’s Contribution Henry Moseley improved periodic table by placing them in increasing atomic number This made it possible to see exactly how many elements yet to be discovered

Today’s Periodic Table Ordered by increasing atomic number (protons) Organized in rows call periods (1-7 rows) Properties change gradually from 1 row to next Columns on the periodic table are called groups or families (18 groups) Groups contain elements with similar physical and chemical properties Representative elements (8 groups) are from groups 1,2,13-18) Include elements that are metals, nonmetals, metalloids

Today’s Periodic Table Transition elements: elements from group 3-12 All are metals Inner transition elements are below main table and include lanthanide and actinide series (named by series that follows lanthanum and actinium (most are radioactive)

Metals Are solid (with exception of Mercury Hg) Have high melting point Has metallic luster, good conductor of heat and electricity Is malleable (can hammer it) Is ductile (can be stretched)

Nonmetals and metalloids Nonmetals are usually Gases or brittle solids at room temperature Poor conductors of heat and electricity 17 nonmetals, some are essential for life (O, C,S, N, P, and I) Metalloids are usually: In between metals and nonmetals that share properties of metals and nonmetals

Element Key Shows name of element, symbol, atomic number, atomic mass and the state of matter (gas, liquid or solid)

Symbols for the Element One or two letter symbols where the first letter is capitilized, second letter is small letter ie Ca, Pb, Na, Si Some names come from first letter of element, others greek or latin names, some for countries discovered

Representative elements Groups 1 and 2 Both groups are active metals (except H) because they easily combine with others substances H shares properties with these groups

Alkali metals Group 1 Silvery solids with low density and low melting points As move down the column they become more reactive Include Li,Na,K,Rb,Cs, Fr

Alkaline Earth Metals Group 2 Denser, harder and higher melting point than group1 (alkali) Are reactive, but not as much as alkali metals

Groups 13-18 Group 13 Boron Family Group 14 Carbon Family all are metals except B which is a metalloid Cookware is made from B, Al for cans,Ga used in computer chips Group 14 Carbon Family C is nonmetalic, Si and Ge are metalloids, Tn and Pb are metals Semi conductors in computers are made from Si because they conduct some electrical current but is buffered to help maintain certain levels of conductivity

Groups 13-18 Group 15: Nitrogen groups N,P,As,Sb,Bi (nonmetal,metalloid, and metals) Nitrogen composed of 78% of atmosphere yet it can’t be utilized by organisms until it is change to nitrates Nitrogen fixing bacteria on roots of organisms can fix nitrogen into nitrates

Groups 13-18 Group 16 Oxygen Family O and S are essential for life Te and Po are both metalloids 20% earths atmosphere is made of O Needed for respiration for energy production of animals O is needed for combustion, ozone layer protects us from ultraviolet radiation S is solid, yellow nonmetal, used in sulfuric acid, production of fertilizers, rubber etc Se is important as trace minerals, conducts electricity

Groups 13-18 Group 17 Halogen family All are nonmetals except At radioactive metalloid Halogen means salt-former like NaCl All halogens make salt As move down the group they become less active

Groups 13-18 Group18 The Noble Gases All are gases, do not react with other elements Uses include the Neon lights in advertisments Electricity passes through tubes containing noble gases that when mixed with noble gases produces different colored lights Bottom of group is radioactive Ra

Transition Elements Metals in the Middle: groups 3-12 Iron Triad (similar properties) Iron Fe, cobalt Co, and nickel Ni Fe used with other metals and C to form alloys like steel Uses of Transition Elements Higher melting points, used in filaments of lightbulbs: tungsten W has highest melting point (3410℃) Mercury Hg, lowest melting point -39℃ Platinium group Ru,Rh, Pa, Os, Ir, Pl similar properties Catalysts are substanes that can make something happen faster but doesn’t change themselves (platinium group)

Inner Transition Element Lanthanides series: rare earths because not found commonly on earth Soft metals, hard to tell apart in same ores, Ce makes up 50%of an alloy called misch used in flints lighters Actinides series: all are radioactive Th, Pa and U are only ones found in nature Rest are synthetic elements (man made)

Inner Transition Element Dentistry and Dental Material Amalgam (mixture of silver, copper, tin, and mercury) is the silver filling Nickel and titanium alloys are used in wires on braces