the third period contains only 8 elements even though the electronic capacity is 18
give scientific reason
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Heya
In the third period only those elements go in whose balance shell is 'M' shell. Or those elements which have only three shells.
The capacity of m shell, as you said, is 18
But after 8 electrons go in to the third shell, the next one goes to the 4th shell.
4s orbital is of lower energy than of 3d. Electrons should first fill the orbitals of lower energy.
After 8 electrons go into 3rd shell, the next two electrons go into the 4th shell. The rest 10 electrons get back to the 3rd shell.
So, only 8 elements have m shell as their valance shell. Third period has only 8 elements in it.
The rest 10 elements, have 4th shell as their valance one.
Hope it helps!
In the third period only those elements go in whose balance shell is 'M' shell. Or those elements which have only three shells.
The capacity of m shell, as you said, is 18
But after 8 electrons go in to the third shell, the next one goes to the 4th shell.
4s orbital is of lower energy than of 3d. Electrons should first fill the orbitals of lower energy.
After 8 electrons go into 3rd shell, the next two electrons go into the 4th shell. The rest 10 electrons get back to the 3rd shell.
So, only 8 elements have m shell as their valance shell. Third period has only 8 elements in it.
The rest 10 elements, have 4th shell as their valance one.
Hope it helps!
Shravniumare:
plz can you give me a short answer in 5to 10 lines
Elements whose valance shell is m are present in the third period. Though the capacity of m shell is 18, there ain't 18 elements in the third shell. This is because, by Aufbau's principle, electrons should be filled in the orbitals in their increasing order of energies. 4s orbital has lower energy than 3d orbital i.e the electrons fill in this order 3s<3p<4s<3d. So 8 electrons fill the 3s and 3p orbitals then fill the orbital in the 4th shell.
Answered by
15
Answer:
Actually 3rd shell should contains 18 elements but there are 10 electrons which are found to have high energy equivalent to energy of 4th shell. So these electrons are not counted in the 3rd shell. Hence, only 8 electrons are in 3 rd shell resulting 2, 8, 8, 18, electronic configuration.
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