Write the electronic configuration of two elements P (atomic number 17) and Q (atomic number 19) and determine their group numbers and period numbers in the Modern Periodic Table.
Atomic number of P=17
Group number = 10 + Number of electrons in outermost shell = 10 + 7 = 17
Since there are 3 shells, it belong to the third period
Atomic number of Q=19
Since number of shells = 4, Group number = Number of electrons in outermost shell = 1
Since there are 4 shells, it belongs to the fourth period .