NCERT Solution for Class 10 Science Chapter 5
Periodic Classification of Elements
NCERT Books for Session 2022-2023
CBSE Board and UP Board
Exercises Questions
Page No-91
Questions No-5
An atom has electronic configuration 2, 8, 7. What is the atomic number of this element?
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(a) The atomic number of this element is 17.
(b) It would be chemically similar to F(9) with configuration as 2, 7.
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(a) The atomic number of the given element is 2 + 8 + 7(= 17).
(b) It would be chemically similar to fluorine [F(9)] because its electronic configuration is 2, 7.
(a) 17
(b) F (9) Fluorine (As fluorine has valence electron equal to seven)