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Q: In the first period, both elements have valence electrons in ………….
  • A. K shell
  • B. M shell
  • C. N shell
  • D. L shell
Correct Answer: Option A - Elements present in the first period = H and He Number of electrons present in Hydrogen atom = 1 Number of electrons present in Helium atom = 2 An atom can have a maximum of 2 electrons in its K shell. Hence, atoms of both elements of the first period have K shell electrons.
A. Elements present in the first period = H and He Number of electrons present in Hydrogen atom = 1 Number of electrons present in Helium atom = 2 An atom can have a maximum of 2 electrons in its K shell. Hence, atoms of both elements of the first period have K shell electrons.

Explanations:

Elements present in the first period = H and He Number of electrons present in Hydrogen atom = 1 Number of electrons present in Helium atom = 2 An atom can have a maximum of 2 electrons in its K shell. Hence, atoms of both elements of the first period have K shell electrons.