Quantum number

Quantum number ,Azimuthal ,Principal

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Quantum numbers

Question1: What is value of Principal & Azimuthal Quantum Number of e’s of 3d subshell.

Ans.     n=3, l=2

Question2. What is the orbital of e with quantum numbers-

n=4,     l=3,      m=0,    s=-1/2

Ans.     4f

Question3.Which set the quantum number is not possible?

n          l           m         s

(a)        3          2          -2         +1/2

(b)        4          0          0          -1/2

(c)        3          2          -3         +1/2

(d)       5          3          0          -1/2

Ans.     (c) is not possible because if l=2 then values of m= -2,-1,0,+1,+2

  1. Which set of Q. No. is not possible?
  2. a) n=1,     l=1,     m=1,    s=+1/2
  3. b) n=1,     l=0       m=1,    s=+1/2
  4. c) n=1,     l=0,      m=0,    s=-1/2
  5. d) n=2,     l=0       m=0     s=+1/2

Ans.     (a)& (b) are not possible because, n=1, then l=0 to (n-1)

so if n=1, then l=0

if l=0, then m=-l to +l including zero, if l=0, m¹1

Question 4.What is the maximum No. of Electrons present in the subshell for n=3,l=1.

Ans.     if n=3, l=1, then subshell is 3p.

p- subshell accommodate        6 electrons

Question5.How many orbitals are possible for n=3?

Ans.     If n=3, l=0,1,2 means s,p,d

s- subshell= One s-orbital

p-subshell = Three p-orbital

d-subshell = Five d-orbital

Question6.Write the possible values of l,m& s for the Principal Q. No. n=1

Ans.     If n=1 then value of l=0 to (n-1)


for l=0, m=0

for m=0, values of s=+1/2 & -1/2

n=1, l=0, m=0, s=+1/2 & -1/2

Question7 .Write the values of l & m for n=2

Ans.     If n=2, l=0 to (n-1)

= 0,1

Values of m=-l to +l including zero.

for l=0, m=0

l=1, m=-1,0,+1

Question8.Write the value of m for l=3

Ans.     Values of m= -l to +l including zero

m= -3, -2,-1, 0,+1, +2,+3

  1. For n=3, Write the values of l & m.

Ans.     n=3, l=0,1,2

If l=0, m=0

l=1, m=-1,0,+1

l=2, m=-2,-1,0,+1,+2

Question9. Write all the possible values of l, m & s for n=3

Ans.             n =3

0 (s-subshell)        0                ±1/2

  1 (p-subshell)      -1  ,0,+1        ±1/2 for all values

2(p-subshell)       -2 ,-1,0,+1,+2           ±1/2 for all values

Question 10. Calculate maximum Number of e’s in n=4

Total electrons = 2+6+10+14=32

Question 11. What information does 3d5 give about Q. No.?

Ans.     for 3d5

n=3, l=2 and five electrons are present in d-subshell

Question 12.What information does 2s2 give about Q. No.?

Ans.     for 2s2

n=2, l=0 and two electrons are present in s-subshell

Question13.Write the values of n & l for the following subshell

a) 3s (b) 5p (c) 4d,  (d) 4f

Ans.     (a) for 3s: n=3, l=0

(b) for 5p : n=5, l=1

(c) for 4d : n=4, l=2

(d) for 4f : n=4, l=3

Question14.Write the values of four Q nos for all the 2s2 electrons

Ans.     For 2s electrons:

for First  e       n=2,     l=0,      m=0,    s=+1/2

for second e    n=2,     l=0,      m=0,    s=-1/2

Question15.Write the values of four Q. Nos. for all the 3p6 electrons


Electrons      1,4   2,5    3,6

for First e        :           n=3,     l=1,      m=-1, s=+1/2

for Second e    :           n=3,     l=1,      m=0,    s=+1/2

for Third e       :           n=3,     l=1,      m=+1, s=+1/2

for Fourth        :           n=3,     l=1,      m=-1,   s=-1/2

for fifth e        :           n=3,     l=1,      m=0,    s=-1/2

for sixth e        :           n=3,     l=1,      m=+1, s=-1/2

Question16. Write the Q. Nos. for the electron of highest energy in calcium & sodium

Ans.     20Ca :1s2,2s2,2p6,3s2,3p6,4s2

Highest energy electron is Ca is 4s2

n=4,     l=0,      m=0,    s=-1/2

11Na :1s2,2s2,2p6,3s1

Highest Energy electron in Na is 3s1

n=3,     l=0,      m=0,    s=+1/2

Question 17.Write all the four Q. Nos. of 5th electron of 3d10


n=3,     l=2,      m=+2,  s=+1/2

Question 18.Write all the four Q. Nos. of 10th& 20th electron of Ca

Ans.     20Ca–1s2,2s2,2p6,3s2,3p6,4s2

10th electron;

n=2,     l=1,     m=+1,  s=-1/2

20thelectron :

n=4,     l=0,      m=0,    s=-1/2

Question 19. Write all the four Q. Nos. of all the electrons present in the d-orbitals of 24Cr.

Ans.     1s2,2s2,2p6,3s2,3p6,4s1,3d5

for 3d1e           :           n=3,     l=2,      m=-2,               s=+1/2

for 3d2 e          :           n=3,     l=2,      m=-1,               s=+1/2

for 3d3 e          :           n=3,     l=2,      m=0,                s=+1/2

for 3d4 e          :           n=3,     l=2,      m=+1,  s=+1/2

for 3d5 e          :           n=3,     l=2,      m=+2,  s=+1/2

Question 20. How are the following subshell represented?

a) n=2, l=1, b) n=4, l=3,                 c) n=3, l=2                   d) n=5, l=0


a) n=2      Second shell                b)   n=4, Fourth shell

l=1       p-subshell                                l=3 means f-subshell

2p                                                        4f

c) n=3,     l=2                               d)    n=5, l=0

l=2 means        d-subshell                    l=0 means s-subshell

3d                                                        5s