Question

How does the electronics confrigration of atom relate to its postion in the modern periodic table

Answer 1

To know its position in periodic table first we should know the electronic configuration of the element.
For example Oxygen.
Atomic number of Oxygen is 16
Electronic configuration of oxygen - 2 8 6.
Valence electrons:  The electrons, which are present in the outermost shell of an atom are called valence electrons.
For any element number of valence electrons is equal to its group number. Here oxygen contains 6 valence electrons hence, it belongs to VI A group.
For any element the valence shell number  is equal to its period number.
In oxygen 3rd shell is the outermost shell (Valence shell) hence, it belongs to period 3.

Answer 2

 the properties of the elements are periodic functions of their atomic number by modern periodic law ,so by the atomic number we can make it electronic configuration of an atom which relate to its position