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. There are 7 periods in the periodic table.

Groups Groups are vertical columns. There are 18 groups in the periodic table.

Groups (cont.) The groups can also be labeled 1A – 8A This helps us to determine valence electrons.

Metals

Physical Properties of Metals Conduct heat & electricity Malleable Ductile Lustrous Almost all metals are solid at normal temperatures. The exception is Mercury, Hg, which is liquid at room temperature.

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 They have an intermediate level of conductivity and thus they make good semiconductors Show a mixture of metallic & nonmetallic properties Shiny or dull Ductile Brittle

Alkali metals  

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  

Alkaline earth metals Metals Silvery-white color Highly reactive Shiny

Transition metals  

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

Halogens  

Halogens All halogens exist as diatomic molecules F2, Cl2, Br2, I2 Fluorine (F2) exists as a poisonous pale yellow gas Chlorine (Cl2) exists as a poisonous pale green gas Bromine (Br2) exists as a toxic brownish liquid Iodine (I2) exists as a black shiny solid that when heated forms a violet vapor

Noble Gases  

Noble Gases Noble gases are Inert – which means that they are unreactive and do not readily combine with atoms of other elements All Noble gases exist as monatomic gases Low melting points Colorless, odorless, tasteless Low densities

Lanthanides  

Lanthanides Strong and durable Magnetic Used to make lasers, sunglasses, and magnets

Actinides  

Actinides Unstable Most of these elements are produced by nuclear reactions Used in nuclear reactors to produce energy Used in nuclear weapons Used as a radioactive technique to determine the age of fossils