B. Answer the following questions: 1. How many electrons with quantum number l =

Question

B. Answer the following questions:

1. How many electrons with quantum number l = 0 are there in the ground state electron configuration for rubidium?

2. How many electrons can have both quantum numbers n = 3 and l = 2?

3. How many unpaired electrons are there for bromine in its unexcited state?

4. What is the abbreviated electronic configuration for V3+?

5. What element is represented by the electron configuration 1s2 2s1 2p5 3s2 3p 2? Is this an electron configuration for this element in its unexcited state?

Explanation / Answer

1. How many electrons with quantum number l = 0 are there in the ground state electron configuration for rubidium?

Solution :- Atomic number of Rubidium is 37

Therefore electronic configuration is [Kr]5s1

l = 0 means orbital is s orbital

therefore it will have 1s2 ,2s2, 3s2,4s2 and 5s1 orbitals

therefore total electrons with l=0 are 2+2+2+2+1 = 9

2. How many electrons can have both quantum numbers n = 3 and l = 2?

Solution :-

n=3 means 3rd shell and l=2 means 3d orbital therefore

electrons which can have both n=3 and l=2 are 10 electrons

3. How many unpaired electrons are there for bromine in its unexcited state?

Solution :-

Bromine (Br) atomic number = 35

Electronic configuration of the Br is [Ar] 3d10 4s2 4p5

P orbital can have maximum 6 electrons

In the Br we have 4p5 electrons means 1 p orbital is having unpaired electron

Therefore number of unpaired electrons in the Br is 1

4. What is the abbreviated electronic configuration for V3+?

Solution :-

Atomic number of the V is 23 therefore neutral atom will have 23 electrons

But V^3+ is formed after losing 3 electrons

Therefore V^3+ have 23-3 = 20 electrons

Therefore electronic configuration of the V^3+ = [Ar] 3d2

1 electron is loosed from 3d and 2 electrons are loosed from 4s orbitals

5. What element is represented by the electron configuration 1s2 2s1 2p5 3s2 3p 2? Is this an electron configuration for this element in its unexcited state?

Solution :- total number of electrons = 2+1+5+2+2 = 12

So the element with 12 electrons is the Mg

But the electron configuration of the ground stat Mg is 1s2 2s2 2p6 3s2

Therefore the given electronic configuration is not in unexcited state. (it is excited state electronic configuration)

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