The Periodic Table of ElementsDmitri Mendeleev (grouped according to
increasing atomic mass)Lighter at top, heavier at bottom
Periodic: happening at regular intervalsPattern that repeats every 7 elements (like the
days of the week)
Elements are arranged on the periodic table according to their atomic number and chemical properties
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Classes of Elements
Elements classified according to their properties as metals, nonmetals, and metalloids
Electrons in outer energy level (valence electrons) help determine element’s category
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Metals(green)
Left of the zigzag line
Few electrons in outer energy ring
Most solid at room temperature
Properties: shiny; ductile; malleable; good conductors electricity/thermal energy
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(Green)
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Nonmetals(orange)Right of the zigzag
Almost complete set of electrons in outer level
More than half are gases at room temperature
Many have opposite properties of metals (ie- dull; brittle; poor conductors of electricity/thermal energy)
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(Orange)
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Metalloids(purple)Border the zigzag
Also called semimetals
About half complete set of electrons in outer level
Properties of both metals and nonmetals
Ex. Boron – hard like a diamond; very brittle; good conductor of electricity
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(Purple)
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Chemical Symbols
Symbols usually one or two lettersFirst letter always capitalizedOther letters always lowercase
Color of the chemical symbol indicates physical state of element at room temp.
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Atomic number
Chemical symbol
Element name
Atomic mass
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PeriodsEach horizontal row from left to right on the
periodic tableProperties follow a repeating pattern
Physical and chemical properties change across each period
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GroupsEach vertical column from top to bottom on
the periodic table
Have similar chemical and physical properities
Also called a family
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Group 1: Alkali Metals
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Group 1Group Contains: MetalsValence Electrons: 1Reactivity: Most reactive metals
Can easily give away one electron from outer level
Only found combined with other elements in nature
Compounds have many uses Sodium chloride (table salt)
Does not include Hydrogen!
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Group 2: Alkaline-Earth MetalsGroup Contains: MetalsValence Electrons: 2Reactivity: Very reactive
Not as easy to give away 2 electrons when combining
Cement, chalk, humans
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Group 2
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Groups 3-12: Transition MetalsGroup Contains: MetalsValence Electrons: 1 or 2Reactivity: Less reactive than alkaline-earth
metalsAlso contain lanthanides and actinides
Good conductors of thermal energyEx. Mercury (thermometers), gold, titanium, iron
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Group 13: Boron GroupGroup Contains: One metalloid & 5
metalsValence Electrons: 3Reactivity: Reactive
Ex. Aluminum
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Group 13
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Group 14: Carbon GroupGroup Contains: One nonmetal,
2 metalloids & 3 metalsValence Electrons: 4Reactivity: Varies
Ex. Carbon - found in proteins, fats, carbohydrates, diamonds
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Group 14
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Group 15: Nitrogen GroupGroup Contains: 2 nonmetals,
2 metalloids & 2 metalsValence Electrons: 5Reactivity: Varies
Nitrogen is 70% of air (not very reactive)
Phosphorus extremely reactive(on box to light matches)
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Group 15
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Group 16: Oxygen GroupGroup Contains: 3 nonmetals, 1 metalloid &
1 metalValence Electrons: 6Reactivity: Reactive
Oxygen is 20% of air (necessaryfor things to burn)
Sulfuric acid is most widely used compound in chemical industry
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Group 16
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Group 17: HalogensGroup Contains: nonmetalsValence Electrons: 7Reactivity: Very reactiveOnly need to gain one electron to
have full outer ring (almost complete set)
Quick to combine with metalsto form a salt
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Group 17
Chlorine (gas)
Bromine (liquid)
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Group 18: Noble GasesGroup Contains: nonmetalsValence Electrons: 8Reactivity: Unreactive
Full set of 8 electrons in outer level
Sometimes called inert gases
Argon used in light bulbs doesn’t react with hot metal filament
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Group 18
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