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

Electronic configuration=2,8,7

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

Electronic configuration=2,8,8,1

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 .

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CA Maninder Singh is a Chartered Accountant for the past 14 years and a teacher from the past 18 years. He teaches Science, Economics, Accounting and English at Teachoo