State and explain Pauli's Exclusion Principle. from Chemistry S

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 Multiple Choice QuestionsShort Answer Type

221.

What subshells are possible in n = 3 energy level?

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222. What is the lowest value of n that allows g orbitals to exist ?
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223.

Using s, p, d notations describe the orbital with the following quantum numbers :
(a) n = 1, l = 0,
(b) n = 3, l = 1,
(c) n = 4, l = 2,
(d) n = 4, l = 3. 

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 Multiple Choice QuestionsLong Answer Type

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224.

State and explain Pauli's Exclusion Principle.


Pauli’s Exclusion Principle: It states: No two electrons in an atom can have the same set of all the four quantum numbers (n, l, m, s).
According to this principle, two electrons in an atom can have a maximum of three quantum numbers identical but the value of the fourth quantum number must be different. Electrons having the same set of values n, l and m are said to belong to the same orbital.
For example, for K shell i.e. when n = 1



Thus, we conclude from the above that:
(i) an orbital cannot have more than 2 electrons, (ii) if an orbital has two electrons, they must have opposite spin.

Application of Pauli’s Exclusion Principle: The maximum number of electrons in different sub-shells and energy levels can be deduced from this principle.
For L shell (n = 2)

n

l

m

s

2

2

2

2

2

2

2

2

0

0

1

1

1

1

1

1

0

0

-1

-1

0

0

+1

+1

+1/2

-1/2

+1/2

+1/2

-1/2

-1/2

+1/2

-1/2


The second energy level (L-shell) can contain maximum 8 electrons. 
2 in l = 0 i.e. s-subshell
6 in l = 1 i.e. p-subshell
Similarly, it can be easily shown that third energy level (M shell) can contain maximum 18 electrons.
2 in  s subshell
6 in p subshell
10 in d subshell
Similarly, it can be easily shown that fourth energy level (N shell) can contain maximum 32 electrons.
2 in s subshell
6 in p subshell
10 in d subshell
14 in f subshell

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 Multiple Choice QuestionsShort Answer Type

225. Why Pauli’s exclusion principle is called exclusion principle?
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226. Why in the building of the atom, the filling of 4s orbital takes place before 3d orbital?
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 Multiple Choice QuestionsLong Answer Type

227. Describe Aufbau Principle.
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228.

Discuss the shapes of s-orbitals.

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 Multiple Choice QuestionsShort Answer Type

229. Give three points of difference between 1s and 2s orbitals.
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230.

The bromine atom possesses 35 electrons. It contains 6 electrons in 2p orbital, 6 electrons in 3p orbital and 5 electrons in 4p orbital. Which of these electron experiences the lowest effective nuclear charge? 

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