Six elements of periodic table A, B, C, D, E and F have atomic numbers of 2, 12, 20, 18, 4 and 10 respectively (where A, B, C, D, E and F are not the chemical symbols of these elements). Based on this information, answer the following questions : Which of these elements belong to the same groups of the periodic table? Why?

Six elements of periodic table A, B, C, D, E and F have atomic numbers

1.	Six elements of periodic table A, B, C, D, E and F have atomic numbers of 2, 12, 20, 18, 4 and 10 respectively (where A, B, C, D, E and F are not the chemical symbols of these elements). Based on this information, answer the following questions : Which of these elements belong to the same groups of the periodic table? Why?
Answer» Solution :First of all, write the electronic configurations of all the given six elements as follows: (1) (i) Elements B, C and E belong to the group 2 of the periodic table because all of them have an equal NUMBER of valence electrons equal to 2. (ii) Elements A, D and F also belong to the group 18 because they are all inert GASES having completely FILLED outermost electron shells with 8 valence electrons.