History of the Periodic Table Empedocles and Aristotle: 5 elements 1. Earth (cold and dry) solid 2. Water (cold and wet) liquid 3. Air (hot and wet)gas 4. Fire (hot and dry) heat 5. Aetherthe divine substance that makes up heavenly spheres and heavenly bodies
History (cont’d) • Lavoisier first to compile a list of known elements (33) • Berzelius developed a system of chemical symbols
Dmitri Mendeleev The first periodic table was arranged by Dmitri Mendeleev in 1869 elements were arranged by increasing atomic mass and grouped according to similar properties Father of the Periodic Table
Henry Moseley • In 1913, Henry Moseleyrearranged Mendeleev’s periodic table according to atomic number. He correctly determined that this is the most fundamental to chemical properties. • We still use this table!!
More Definitions… Atomic number (Z): number of protons in the nucleus of the atom “fingerprint” of the atom -the identity of the atom is determined by the atomic number Atomic mass: (mass number) total number of protons and neutrons in the nucleus of the atom
Periodic Law Properties of elements tend to change in a regular pattern when elements are arranged in order of increasing atomic number
The periodic table can be organized several different ways…. • periods/groups • metals/nonmetals/ metalloids • cations /anions
Groups or Families A column (the things up and down) in the periodic table Elements within the same group tend to have similar properties also similar electron configurations
Groups/Families Group 1: Alkali metals -very reactive, soft metals Group 2: Alkali-earth metals Groups 3-12: Transition metals -not very reactive Group 17: Halogens Group 18: Noble Gases -nonreactive
Periods A row (left to right) in the periodic table Lanthanides Rare Earth Actinides Metals
Metals • Element that is a good conductor of heat and electricity • at left and center of periodic table • Malleability: property of a metal by which it can be hammered or rolled into sheets • Ductile: ability of metals to be drawn into fine wire • Luster: ability of a metal to shine
Nonmetals An element that is a poor conductor of heat and electricity Brittle!!! Most of these are gases are room temperature N2, O2, F2, Cl2 Hg and Br only liquids!!! Ex. Phosphorus: too reactive to exist in pure form in nature -All living things contain phosphorus!
Metalloids An element that has some properties of metals and some characteristics of nonmetals Less malleable than metals, but less brittle than nonmetals Some have luster Semiconductors
Noble Gases Group 18 elements UNREACTIVE!!! Ne, Ar, Kr, Xe all used in lighting Helium (He) is used in party balloons because less dense than air
Halogens Group 17 Very reactive!!! F is most reactive element