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The Periodic Table
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Introduction to the Periodic Table
By 1830, there were 55 different elements, used for many different things Today, there are 118 identified elements with more to come! 2
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Dmitri Mendeleev Arranged elements in order of increasing atomic mass
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Mendeleev’s table created in 1869 Mendeleev noticed that elements with
similar properties fell into groups on the periodic table 4
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Fun Fact! In his final version of the periodic table in 1871, Mendeleev left gaps, predicting they would be filled by elements not yet known to scientists. He correctly predicted the properties of these elements
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Henry Moseley Moseley realized that some of the elements
were out of order, so he rearranged the elements according to their atomic number 6
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Today’s periodic table
Elements are organized according to their atomic number Periods – a row of elements in the periodic table whose properties change gradually and predictably
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Today’s periodic table
Group or Family – a column of elements that have similar physical or chemical properties 7
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Zones on the Periodic Table
Representative elements – Groups 1-2 and groups 13-18 Transition elements – Groups 3-12 9
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Metals Solids Luster Good conductor of heat and electricity Malleable
Ductile 10
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Nonmetals Usually gases or brittle solids
Poor conductors of heat and electricity phosphorous sulfur
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Metalloids Have some properties of metals and some of nonmetals
arsenic boron 12
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Element Symbols The symbol for an element must always be written with the first letter capitalized and the second or third as a lower case letter! Cu Cs
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Alkali Metals Group 1 elements – Lithium, sodium, potassium, rubidium, cesium and francium Silvery solids with low densities and low melting points Very reactive elements – from top to bottom of the periodic table rubidium
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Alkaline Earth Metals Group 2 elements – beryllium, magnesium calcium, strontium, barium, radium Denser, harder and have a higher melting point than alkali element in same period strontium 15
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Boron Family Group 13 – all metals except Boron which is a metalloid
Uses: B – cookware Al – cookware, popcans Ga –computer chips Indium wire 16
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Carbon Family Group 14 carbon – nonmetal silicon & germanium
- metalloids tin & lead - metals carbon germanium
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The Nitrogen Family Group 15 includes
nitrogen and phosphorous (nonmetals) Arsenic and antimony (metalloids) Bismuth (metal) antimony
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fun fact Nitrogen is relatively unreactive. Sometimes it is used inside a sealed case to protect valuable documents that might react with oxygen or other gases in air
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The Oxygen Family Group 16 includes
Oxygen, sulfur, selenium (nonmetals) Tellurium, polonium (metalloids)
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The Halogen Family Group 17 Includes
Fluorine, chlorine, bromine, iodine (nonmetals) Astatine (metalloid) Chlorine gas
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Noble Gases Group 18 Includes
Helium, neon, argon, krypton, xenon, radon (nonmetals) This group is very stable
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Transition Elements
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Iron Triad Includes: iron, cobalt, and nickel
All have magnetic properties cobalt iron 24
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fun fact Molecules containing transition elements are important to the life processes of many organisms. Perhaps the most familiar example of this is found in the iron-containing heme complex of hemoglobin, which is responsible for the transport of oxygen in the blood of all vertebrates and some invertebrates
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Transition element vocabulary
Catalyst – a substance that can make something happen faster but is not changed itself Synthetic elements – man-made elements
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Inner Transition Elements
2 groups: lanthanide series – from cerium to lutetium (numbers 58 – 71) actinide series – from thorium to lawrencium (numbers )
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The Lanthanides Characteristics – soft metals thulium terbium
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The Actinide Series Characteristics – radioactive, synthetic elements, metals uranium
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