how does the electronic configuration of an atom relate to its position (period and group)in the modern periodic table?

Modern periodic table is based on atomic numbers.In this periodic table, elements are arranged in increasing order of their atomic numbers.Electronic configuration of an element is obtained from the atomic numbers.It gives the information of valence electrons and number of shell present in the element.
We get the information of group number after knowing valence electrons.For ex- in case of alkali metals which are placed in group 1 of the periodic table because they have 1 valence electron in their valence shell.Similarly for second group elements called as alkaline earth elements.For elements belonging to group number 13 to 18 group number is given by 10 + no. of valence electrons.
Now for period,number of shells present in an element is equal to period number.Thus,by knowing electronic configuration we know the group number and period number of an element, which is the position of element in periodic table.

Approved

Dear student the group no. and periods to which an element belongs are determined by observing the valence electrons and the number of shells respectively.All you know to do this is that remember the atomic numbers and learn how the atomic configuration is done.Once you doing these it becomes easier to determine the group no. as well as the period.The process to determine both i have already explain you.For 13 to 18 group elements this is explained to you that add 10 + no. of valence electron to find the group no..All the very best i am sure you will find the group no. and the period of any particular element.