Hello student,

The modern periodic table, the one we use now, is a new and improved version of certain models put forth by scientists in the 19th and 20th century. Dimitri Mendeleev put forward his periodic table based on the findings of some scientists before him like John Newlands and Antoine-Laurent de Lavoisier. However, Mendeleev is given sole credit for his development of the periodic table.

The periodic table is an arrangement of all the elements known to man in accordance with their increasing atomic number and recurring chemical properties. They are assorted in a tabular arrangement wherein a row is a period and a column is a group.

Elements are arranged from left to right and top to bottom in the order of their increasing atomic numbers. Thus,

• Elements in the same group will have the same valence electron configuration and hence, similar chemical properties.
• Whereas, elements in the same period will have an increasing order of valence electrons. Therefore, as the energy level of the atom increases, the number of energy sub-levels per energy level increases.

The first 94 elements of the periodic table are naturally occurring, while the rest from 95 to 118 have only been synthesized in laboratories or nuclear reactors.

I hope this helps, All the Best!

Hai, aspirant, in modern periodic table elements are arranged in order of their increasing atomic numbers, the vertical column are known as groups and horizontal column known as periods. There are 18 groups and 7 periods in the modern periodic table, elements having same number of valence electrons are placed in the same group let's take an example elements having valence electron 3 are placed in group 13 , elements having same number of shells are placed in same period
In 1913,Henery Moseley shows that atomic numbers of an elements is a more fundamental property than it's atomic  mass. The physical and chemical properties of elements are the periodic function of their atomic numbers of elements. Modern periodic table is based on atomic numbers of elements
Atomic numbers is equal to number of protons present in the nucleus of an atom of an elements.

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