RRB RPF RPSF SI and CONS Model Papers 8 with solutions

(3) The periodic properties of an element depend on valency and number of shells in an atom. As we move down a group the number of shell increases successively such that the number of the shell of an element is equal to the number of periods to which it belongs. As we move across a period, the number of shell remains the same. For example, elements of the second period have two shells.