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Chem Chemistry

ChemistryNEB 2074 (old course) (grade increment)

Calculate the atomic number and number of p electrons of an atom whose valence shell electronic configuration is 4S^2 .

2

Answer

· Based on the official syllabus and past papers
Updated

The valence shell electronic configuration indicates that the atom has electrons filling the 4th shell, specifically in the s-subshell.

Step 1: Determine the atomic number

  • The configuration means the outermost shell is the 4th shell.
  • The maximum number of electrons in the 4th shell is (4s, 4p, 4d, 4f).
  • However, since only the 4s subshell is filled, the atom must belong to Group 2 (Alkaline Earth Metals) of the periodic table.
  • The 4s subshell fills before the 3d subshell, so the atom is in Period 4.
  • The element with as its valence configuration is Calcium (Ca).
  • The atomic number of Calcium (Ca) is 20.

Step 2: Determine the number of p-electrons

  • The p-subshell in the 4th shell () is empty in Calcium.
  • Therefore, the number of p-electrons in the valence shell is 0.

Final Answer:

  • Atomic number = 20
  • Number of p-electrons = 0

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