MODERN PERIODIC TABLE

After the discovery of large number of elements they were to group in families showing max resemblance. So the elements were grouped in the form of table in which properties of elements were repeated after regular intervals.

CLASSIFICATION

Earlier chemists, scientist arranged elements on the basis of valency, metallic & non-metallic character. Scientists like Dobereiner[1815-1829],Newland[1864],,Mendeleeff[1869] arranged elements in the increasing order of their At.wts. [atomic weights].Moseley[1912] arranged elements in the increasing order of their At. no.[atomic number] in a modified table called Modern Periodic Table[M.P.T].

Arrangement of elements in the M.P.T. is based on the Modern Periodic Law, which states that –Physical & Chemical properties of elements are based on At. no. & not.At.wt. IMPORTANT FEATURES OF M.P.T. SYSTEMATIC ARRANGEMENT- elements are arranged in increasing order of their At. no. in horizontal rows called “Periods” & vertical columns called “Groups”. PERIODS-M.P.T. has 7 periods. Each period starts with a Alkali metal having 1 electron in it’s outermost shell & ends with 0 group noble gases having completely filled outer shell [8 electrons].

GROUPS-M.P.T. has 18 groups. Each group has same outermost shell configuration having similar properties.18 groups are-I—VII,VIII & 0.Groups I—VII are subdivided into A & B.

GROUP-IA-ALKALI METALS- React with water forming strong alkalis-Lithium, Sodium, Potassium, Rubidium, Caesium, Francium.

GROUP-IB-COINAGE METALS-Used to make coin-Copper,Silver,Gold.

GROUP-IIA-ALKALINE EARTH METALS-React with water forming strong alkalis-Berilium, Magnesium, Calcium, Strontium, Barium,Radium.

GROUP-VIIA-HALOGEN GROUP-Found under sea, highly electronegative-Fluorine,Chlorine,Bromine,Iodine.

GROUP-0-NOBLE GASES-Chemically inert & non-reactive in chemical reactions-Helium, Neon, Argon, Krypton,Xenon,Radon

[GROUP-IIIB TO GROUP-VIIB-TRANSITIONAL METALS]-Have ‘d’ electrons, Paramagnetic in nature, Colourful

[GROUP-IA TO GROUP-VIIA-NORMAL ELEMENTS]-Half filled ,consists of metals & non-metals.