Question

Who arranged the modern periodic table? How is it arranged?

Answer 1

In past scientists assumed that the properties of the elements mainly depended on their atomic masses and on this assumption Mendeleev proposed a periodic table in which 63 elements were placed in a vertical column called groups and in horizontal rows called periods.

Complete answer:
Mendeleev’s periodic table is rejected as it is not able to explain the position of certain elements like rare earth metals and isotopes. This defect was removed by the scientist named Henry Moseley and he discovered the modern periodic table.
Modern periodic table consists of 18 vertical columns known as groups arranged as left to right and seven horizontal rows known as periods arranged from top to bottom. In this periodic table elements are arranged according to their atomic number and this table divides the elements into s, p, d and f-block elements on the basis of their valence shell electrons.
Group 1,2,13-17 are known as main group elements in which the last electron will enter in s or p subshell, group 3-12 are known by the name transition elements and also called d-group elements and group 18 is of inert gases or noble gases i.e. those elements which have fully filled outermost atomic shell and have high stability. Rather than this there are two rows below the table known as inner transition elements in which the last electron will enter into f-subshell.

Note:
There are also two main demerits of modern periodic table i.e. it will not be able to define the position of hydrogen atom and also elements which have the same properties like barium-lead and copper-mercury are put separately.