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The Periodic Table

Chemistry

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Origin of Periodic TableTriads - groups of 3 elements with

similar properties

(Dobereiner – 1817)

Law of Octaves – properties of elements repeat every 8 elements

(Newlands – 1863)

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Origin of Periodic TableDimitri Mendeleev – 1869

–Properties of elements are periodic functions of their atomic masses.

–Developed 8 column table–Left spaces for undiscovered

elements–Columns contained elements with

similar properties–Problems with Ni, I, K (Why?)

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Origin of Periodic TableX-ray experiments by Mosley

(1913) led to discovery of atomic numbers.

Modern Periodic Law – properties of elements are periodic functions of their atomic numbers.

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Organization of Periodic TableRows are called periods.Columns are called families or

groups.All elements in a family have similar

properties.Octet Rule – elements with 8 valence

electrons are unreactive

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Periodic Table

Rows = Periods

Columns = Families or Groups

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Chemistry Chapter 5Chemistry Chapter 5The Periodic LawThe Periodic Law

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Mendeleev’s Periodic Table

Dmitri Mendeleev

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Periodic Table with Group Names

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Alkali Metals 1st column in blue

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Easily lose valence electron (Reducing agents)

React violently with water Large hydration energy React with halogens to form

salts

The Properties of a Group: the Alkali Metals

H- Hydrogen Rb- Rubidium

Li-Lithium Cs- Cesium

Na-Sodium Fr-Francium

K-Potassium

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Properties of MetalsProperties of Metals Metals are good conductors of heat and electricity

Metals are malleable

Metals are ductile

Metals have high tensile strength

Metals have luster

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Examples of MetalsExamples of Metals

Potassium, K reacts with water and must be stored in kerosene

Zinc, Zn, is more stable than potassium

Copper, Cu, is a relatively soft metal, and a very good electrical conductor.

Mercury, Hg, is the only metal that exists as a liquid at room temperature

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Alkaline Earth Metals 2nd column - green

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Properties of alkaline metals Be, Mg, Ca, Sr, Ba, Ra The alkaline earth metals, or alkaline

earths, are beryllium, magnesium, calcium, strontium, barium, and radium.

Possess many properties of metals Low electro negativities Low electron affinities They have smaller atomic radii than the

alkali metals

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Transition Metals all have similar properties Middle – purple and can give up different amounts of electrons at different times

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Properties of MetalloidsProperties of Metalloids

Metalloids straddle the border between metals and nonmetals on the periodic table.

They have properties of both metals and nonmetals.Metalloids are more brittle than metals, less brittle than most nonmetallic solids Metalloids are semiconductors of electricity Some metalloids possess metallic luster

B- Boron As- Arsenic At- Astatine

Ge- Germanium Te-Tellurium

Sb- Antimony Si- Silicon

Al-Aluminum Po- Polonium

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Silicon, Si – A MetalloidSilicon, Si – A Metalloid

Silicon has metallic luster Silicon is brittle like a nonmetal Silicon is a semiconductor of electricity

Other metalloids include:

Boron, B Germanium, Ge Arsenic, As Antimony, Sb Tellurium, Te

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PropertiesProperties of of NonmetalsNonmetals

Carbon, the graphite in “pencil lead” is a great example of a nonmetallic element. Nonmetals are poor conductors of heat and electricity Nonmetals tend to be brittle Many nonmetals are gases at room temperature

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Examples of NonmetalsExamples of Nonmetals

Sulfur, S, was once known as “brimstone”

Microspheres of phosphorus, P, a reactive nonmetal

Graphite is not the only pure form of carbon, C. Diamond is also carbon; the color comes from impurities caught within the crystal structure

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Non-Metals Right of the stair-step line

C-Carbon, N- Nitrogen, O-Oxygen, P-Phosphorus, Cl-Chlorine, Se-Selenium

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Halogens 7th tall column (light orange) F-fluorine Cl-Chlorine Br-Bromine I- Iodine

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Properties of Halogens a particular class of nonmetals. Very high electronegativities Seven valence electrons (one short of a

stable octet) Highly reactive, especially with alkali

metals and alkaline earths Halogens range from solid (I2) to liquid

(Br2) to gaseous (F2 and Cl2) at room temperature.

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Noble Gases last tall column (yellow) He-Helium Ne-Neon Ar-Argon Kr-Krypton Xe-Xenon

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Properties of Noble gases

Unreactive gases Odorless Colorless All produce light when an electric

current is applied

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Lanthanides – Ce row Actinides – Th row

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Half of the distance between nucli in covalently bonded diatomic molecule

"covalent atomic radii"

Periodic Trends in Atomic Radius

Radius decreases across a period Increased effective nuclear charge dueto decreased shielding

Radius increases down a group Addition of principal quantum levels

Determination of Atomic Radius:

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Table of Table of Atomic Atomic RadiiRadii

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Increases for successive electrons taken from the same atom

Tends to increase across a period

Electrons in the same quantum level do not shield as effectively as electrons in inner levels

    Irregularities at half filled and filled sublevels due to extra repulsion of electrons paired in orbitals, making them easier to remove

Tends to decrease down a groupOuter electrons are farther from thenucleus

Ionization Energy - the energy required to remove an electron from an atom

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Affinity tends to increase across a period

Affinity tends to decrease as you go down in a period

Electrons farther from the nucleusexperience less nuclear attraction

Some irregularities due to repulsive forces in the relatively small p orbitals

Electron Affinity - the energy change associated with the addition of an electron

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Table of Electron AffinitiesTable of Electron Affinities

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Ionic RadiiIonic RadiiCations

Positively charged ions Smaller than the

corresponding atomAnions

Negatively charged ions Larger than the corresponding atom

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Summation of Periodic Trends

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Table of Ion Sizes

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ElectronegativityElectronegativity

A measure of the ability of an atom in a chemicalcompound to attract electrons

Electronegativities tend to increase across a period

Electronegativities tend to decrease down a group or remain the same

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Periodic Table of Electronegativities