Classification of Elements and Periodicity in Properties

Modern periodic law and Present form of the periodic table

Modern/Moseley's/Long form of periodic table :

Description of periodic table :

 Period Elements No.of elements Orbitals filled
 1  H and He  2  1s
 2  Li — Ne  8  2s, 2p
 3  Na — Ar  8  3s, 3p
 4  K — Kr  18  4s, 3d, 4p
 5  Rb — Xe  18  5s, 4d, 5p
 6  Cs — Ra  32  6s, 4f, 5d, 6p
 7  Fr →    7s, 5f, 6d, 7p


View the Topic in this Video from 0:11 to 14:13

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1. \tt Atomic\ volume=\frac{molecular\ mass}{density}

2. Atomic weight = Valency × Equivalent weight = Group number × Equivalent weight.