Question 4 - Past Year - 2 Mark Questions - Chapter 5 Class 10 - Periodic Classification of Elements

Last updated at April 16, 2024 by

An element ‘X’ has mass number 35 and 18 number of neutrons. Therefore, Electronic configuration of X= 2, 8, 7. Write atomic number and electronic configuration of ‘X’. Also write group number, period number and valency of ‘X’.

 

Answer

Mass number = 35

Number of neutrons = 18

  • Mass number = number of neutrons + number of protons

Therefore, number of protons = Mass number - number of neutrons

                                                      = 35 - 18 

                                                      = 17

  • Atomic number = number of protons = 17
  • Therefore, the electronic configuration of X is 2, 8, 7
  • Group number = 10 + number of valence electrons = 10 + 7 = 17
  • Since there are 3 shells, period number is 3.
Go Ad-free
Maninder Singh's photo - Co-founder, Teachoo

Made by

Maninder Singh

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