THE HISTORY OF PERIODIC TABLE

The periodic table is invented due to avoid confusion while searching and locate the elements.
at that time chemists are started to frame ways to group these elements and compounds on the basis of their physical and chemical states.

at the beginning of the 18 th century, a scientist called joseph Louis stated that the hydrogen atom is a building material and atoms of all other elements are simply due to a combination of a number of hydrogen atoms. and also considering some examples the atomic weight of hydrogen is taken as ONE.

DOBEREINER'S TRIAD THEORY:

dobereiner's he was a German man. he was tried to prove the relationship between elements of their properties and atomic weights.

• he stated that the arrange the three elements are in ascending order which has similar properties with the help of atomic weights.
• and the middle element is the average of the first and third elements.
• this theory is called the law of triads.

limitations:

this law failed for low mass and very high mass elements.

• according to this theory, the chemists are looking at the physical and chemical properties of elements in terms of groups.

examples: atomic weight

calcium(40),strontium(87.5),barium(137)

mean of atomic weight;[(40+137)/2]=87.5.

NEWLANDS OCTAVE CONFIGURATION:

Newlands proposed that the octave configuration. first, introduce to assign the atomic numbers.

• this theory states that elements are arranged in the ascending order of their atomic weights they fall into a pattern.
• in which their properties repeat at regular intervals.
• every eighth element starting from given a given element resembles in its properties to that of the starting element.
• the elements which have similar chemical properties are to be present along the row. 
• in the Indian musical system sa,re,ga,ma,pa,da,ni. naturally, there must be some repetition of words according to that every eighth element similar to the first one and it is the first one of the next scale.

NOTE: all the non-metals give the acids. and also all the metals give the base.

MENDELEFF'S PERIODIC TABLE:

he is the first chemist that divided the chart into eight vertical columns known as groups.

• he states that the physical and chemical properties of elements are the periodic functions of their atomic weights.
• he tried to prove the similarities of elements in the same group in terms of their common valency.

NOTE: EKA ALUMINUM=GALLIUM

             EKA BORAN        =SCANDIUM

             EKA SILICON      = GERMANIUM

HJ MOSELEY:

• he proposed the modern periodic table.he is the father of modern periodic table.
• he found each element emits an x-ray characteristic pattern when subjected to a bombardment of high energy electrons.
• by analyzing the patterns of x-ray, he was able to calculate the protons in atoms of respective elements.
• the periodic law was changed the atomic weight concept to the atomic number concept in the modern periodic table.
• the atomic number is indicated with the letter 'Z'.

A further brief explanation is in the chemistry fundamental on the left side top widget(pages).

NOTE:

• electronegativity: it is the process of gaining electrons. the high electronegativity power in the periodic table is fluorine(9).
• electropositivity: it is the process of losing the electrons.example: chlorine(17)
• metallic nature is nothing, but loss of electrons.