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Periodic table

                                   Periodic table


ELEMENTS- Elements are pure from of matter that are made up of one type of atom.
·      DOBEREINER- Grouped all elements in three (triads).
·       NEWLAND- Observed that when elements are arranging in increasing order of their atomic mass. Every eighteen element beginning from any element resemble the first element in its physical and chemical properties.
·       DMITRI MENDLEVE- He is a Russian chemist gave the first periodic table of elements based on his law which states that “The properties of elements are the periodic functions of their atomic mass.”  
·       Modern periodic table was given by HENERY MOSELEY.
Periodic table- A tabular form of elements in group and periods highlighting the regular trends in properties of elements is called periodic table.
·       NEIL BOHR- He has given the long form of modern periodic table.
Ø About groups of periodic table-
1.   Group 1. These elements are known as alkali metals.
2.   Group 2. These elements are alkaline  earth metals.
3.   Group 3,4,5,6,7,8,9,10,11 and 12. These elements are transition elements.
4.   Group 13. Boron family.
5.   Group 14. Carbon family.
6.   Group 15. Nitrogen family.
7.   Group 16. Oxygen family.
8.   Group 17. These elements are halogens.
9.   Group 18. These elements are noble gases or inert gases .
Ø Group 3 of sixth and seventh periods have similar properties because they belongs from same groups.
Ø In Group 17 (halogens) all elements have seven electrons in its last orbit.
SHELLS- The path at which electrons revolve that paths are called shells.
VALENCY- The combining capacity of an element is called its valency.
Some important periodic properties are-
Ø ATOMIC SIZE (ATOMIC RADIUS)
Ø METALLIC CHARACTER
Ø NON- METALLIC CHARACTER
Ø IONISATION POTENTIAL(IONISATION ENERGY)
Ø ELECTRON AFFINITY
Ø ELECTRON GATIVITY

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