Basic View Of Periodic Table.

     In earlier 19th century about 30 elements were known and were classified in 3 types as metals, non metals and metalloids. In 1869 Russian chemist Dimitri Mendeleev put 4th periodic table of 63 elements using atomic mass and properties of elements. Meldeleev arranged the elements known at the time in an increasing order of their atomic masses. The orbital number of an element is called its atomic number.

    Mendeleev's periodic table was revised in accordance with modern periodic law and called it modern periodic table. Mendeleev's periodic table is based on atomic mass of an element, modern periodic table is based on Atomic Number of element. Atomic number is related to number of electrons and number of electrons are changed in any reaction. Also chemical properties of atom depends on number of electrons. Hence modern periodic table based on Atomic number.

    There are total 7 horizontal rows and 18 vertical coloumns named as periods and groups respectively. Elements is same group have similar chemical properties reason behind it is same valance electrons. Elements in same period have same number of orbitals but number electrons is different. Based on in which orbital last electron is present periodic table is divided in 4 blocks S, P,  D and F. Group 1 & 2 is called S block, Group 3 to 12 is called D block, Groups 13 to 18 is called P block. The two rows present at bottom is called F block.

    1st group elements are basic elements named as alkaline metals. 2nd group elements are alkaline earth metals. Group 18 elements are called inert gases or noble gases. 17 group elements are salt forming hence they are halogens. 16 group elements are chalcogens. 15 group elements are nictogens. group 11 elements are coingens as they used to make coins. S and P block elements are representative elements except group 18.D block elements are transition elements and F block elements are inner transition elements. 75% elements in periodic table are metals, 8 are semi metals. Left to the semi metals are metals and to right are non metals. 90 elements in periodic table are natural elements and 28 elements are man made.

    There is specific order about properties of elements in periodic table. Atomic radius is decrease from left to right . Ionisation enthalpy and electron gain enthalpy increases from left to right. Electronegativity  increases from left to right. Atomic radius increases from top to bottom. ionisation enthalpy, electronegativity and electron gain enthalpy decreases from top to bottom. There are lots of exception to periodic table but this is just a basic view of periodic table.