The number of valence electrons of P and Si are ______ respectively.

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SSC JE EE Previous Year Paper 15 (Held On: 26 Sep 2019 Evening)
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  1. 3 and 4
  2. 5 and 4
  3. 4 and 4
  4. 4 and 5

Answer (Detailed Solution Below)

Option 2 : 5 and 4
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Detailed Solution

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Mistake Points

The question is asking about the number of valence electrons, and not about the valency of the atom. Since a valence electron is the number of outer shell electrons that is associated with an atom, Phosphorous will have 5, and Silicon will have 4 valence electrons.

The correct answer is 5 and 4.

Explanation:

  • A valence electron is an outer shell electron that is associated with an atom.
  • These electrons can participate in the formation of a chemical bond.

Key Points

  • Silicon has two electrons in its first shell, eight electrons in the second shell, and four (4) electrons in the third shell.
  • Since the electrons in the third shell are the outermost electrons, silicon has four valence electrons.
  • Phosphorus having an atomic number 15 is a pentavalent element, which means it has 5 valence electrons in its outermost shell.
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