ICSE Class 9 Answered
What are 'energy levels'? Explain the arrangement and distribution of electrons in the various shells with reference to an atom in general and t o an atom of potassium '19(atomic number ) and 30(relative atomic mass) of K' with special reference to 2n^2 rule.
Asked by arti | 30 Dec, 2016, 12:55: PM
Expert Answer
The electrons revolve rapidly round the nucleus in fixed circular paths called energy levels or shells.
- According to Bohr’s model, electrons occupy certain stable orbits or shells. Each shell has a definite energy.
- These orbits or shells are represented by the letters K, L, M, N… or the numbers 1, 2, 3, 4…
- The maximum number of electrons present in the shell is given by the formula (2n2), where n is the orbit number or shell number.
- The maximum number of electrons in different shells for potassium is as follows:
Atomic number of potassium = 19
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- The first orbit or K shell will have 2 × 12 = 2 electrons.
- The second shell will have 2 × 22 = 8 electrons.
- The third shell will have 2 × 32 = 8 electrons.
- The fourth shell will have 2 × 42 = 1electron
- The maximum number of electrons which can be accommodated in the outermost orbit is 8.
- Electrons are not accommodated in a given shell unless the inner shells are filled.
Answered by Vaibhav Chavan | 30 Dec, 2016, 04:16: PM
