Periodic Table Organizing the Elements

Antoine Lavoisier (1790s) French Chemist About 23 elements Au, Ag, C, O

Antoine Lavoisier (1790s) Electricity allowed compounds to break down into elements Spectrometer Industrial Revolution – Petrochemicals, soaps, fertilizers, and dyes.

John Newlands (1837- 1898) English – Arrange elements in increasing atomic mass order, properties repeated themselves every eighth element Octet rule

John Newlands (1837- 1898) Octet rule does not apply to Hydrogen and Helium

Lothar Meyer (1830-1895) German Chemist Relationship between Mass and properties

Dmitri Mendeleev (1834-1907) Russian Chemist About 70 elements

Dmitri Mendeleev Predicted the existence and properties of the missing elements Left blanks for them on his table.

Dmitri Mendeleev How did he line up the elements?

Dmitri Mendeleev How did he line up the elements? Increasing atomic mass Similar properties side by side

Dmitri Mendeleev How did he line up the elements? Left blank spaces for unknown elements

Henry Moseley (1887-1915) 1913 British physicist – determined atomic number Lines up atoms by increasing atomic number

Today’s Periodic Table Glenn Seaborg Lanthanides & Actinides

Alkali metals Alkaline earth metals Transition Metals

Alkali metals Alkaline earth metals Transition Metals

Alkali metals Alkaline earth metals Transition Metal

Non-metals Noble gases

Non-metals Noble gases

Non-metals Noble gases Halogens Metalloids

Non-metals Noble gases Halogens Metalloids

Periods – horizontal rows Seven periods Properties change when move across period

Periodic Law Properties repeat from one period to next Periodic Law – periodic repetition of physical & chemical properties

Elements with similar properties are in same column. Group/family- Vertical column 1A, 2A, 3A, etc.

Identified by number & letter Column 1A Identified by number & letter Column 1A ? React vigorously with water (explosive)

Periodic Trends Atomic Radius Decrease Increase

Atoms lose electrons to form cations (positive) Empty orbital Repulsion is less between electrons

Atoms gain electrons to form anions (negative) Repulsion is increased between electrons = cloud gets bigger

Ionic Radius Increases 5A, 6A, 7A all Gain electrons Larger Smaller decreases 5A, 6A, 7A all Gain electrons Increases

Ionization Energy energy required to remove an electron from a gaseous atom.

Ionization Energy – Increases Decreases

Octet Rule – (John Newlands) Atoms tend to gain, lose or share electrons to acquire a full set of valence electrons.

Electronegativity Ability to attract electrons in a chemical bond.

Periodic Trends Electronegativity – Increases Decreases

Reactivity of metals and non-metals Most reactive metal ? Francium low electronegativity

Most reactive non-metal ? Fluorine high electronegativity

Properties Metals – high conductivity & high luster Ductile (pull into wire) Malleable (sheets)

Representative elements 80% of elements are metals Usually solid at room temp. Except? Hg

Non-metals Upper right corner of table Non-lustrous Poor conductors

Non-metals Gas O Cl Brittle solid S Group 7A – Halogens

Non-metals Group VIII A – noble/inert gas undergo very few reactions Heavy stair-step line - metalloids

Non-metals Metalloids – between metals & non-metals Properties between both Si & Ge – computer chips and solar cells

Reactivity of Metals Ability of a metal to undergo a chemical change Lose electrons

Reactivity of Metals decreases INCREASES

Reactivity of Non-Metals INCREASES decreases