Introduction to the Periodic Table

Dmitri Mendeleev The elements were first arranged in the periodic table in 1869 by Dmitri Mendeleev. By arranging all of the 63 elements then known by their atomic weights, he managed to organize them into groups possessing similar properties. Where a gap existed in the table, he predicted a new element would one day be found and deduced its properties.

Periods Periods are horizontal rows.

Groups Groups are vertical columns.

Metals

Physical Properties of Metals Conduct heat & electricity Malleable Ductile Lustrous Almost all metals are solid at normal temperatures.

Nonmetals

Physical Properties of Nonmetals Brittle Not lustrous Poor conductors of heat & electricity Many nonmetals are gaseous at normal temperatures (N, O, Cl, Ne) One nonmetal is liquid at normal temperatures (Br) Several nonmetals are solid at normal temperatures (C, P, S)

Metalloids or semimetals

Physical Properties of Metalloids Show a mixture of metallic & nonmetallic properties They have an intermediate level of conductivity and thus they make good semiconductors

Alkali metals

Silvery colored They are soft, and can be easily cut with a knife to expose a shiny surface which dulls on oxidation. Highly reactive Low melting temperatures Low boiling temperatures Low densities

Alkaline earth metals

Metals Shiny, silvery-white color Highly reactive

Transition metals

Lustrous metallic appearance Many of their compounds are colored Good conductors of heat & electricity High melting points High boiling points

Halogens

All halogens exist as diatomic molecules F 2, Cl 2, Br 2, I 2, At 2

Noble Gases

Noble gases are Inert – which means that they are unreactive and do not readily combine with atoms of other elements Noble gases are monatomic gases Noble gases boil at low temperatures

Lanthanides

Actinides