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Structure of Atom — Chemistry STD 11 Science — Question

Gujarat BoardEnglish MediumSTD 11 ScienceChemistryStructure of Atom5 Marks
Question
A neutral atom of an element has 2K, 8L and 5M electrons. Find out the following:
  1. Atomic number of the element.
  2. Total number of s-electrons.
  3. Total number of p-electrons.
  4. Number of protons in the nucleus.
  5. Valency of the element.
✓

Answer

The electronic configuration of the element with 2K, 8L and 5M electrons will be:
$1\text{s}^2\ 2\text{s}^2\ 2\text{p}^2_\text{y}\ 2\text{p}^2_\text{z}\ 3\text{s}^2\ 3\text{p}^1_\text{x}\ 3\text{p}^1_\text{y}\ 3\text{p}^1_\text{z}$
  1. Total number of electrons = 2 + 8 + 5 = 15
$\therefore$ Atomic number of the element = 15
  1. Total number of s-electrons = 2 + 2 + 2 = 6
  2. Total number of p-electrons = 6 + 3 = 9
  3. Since, the atom is neutral,
$\therefore$ Number of protons = Number of electrons = Atomic number = 15
  1. Since, the element has only half-filled atomic orbitals, therefore, valency of the element = 3.

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