UNIT 2: Quantum Mechanical Model of Atom - Online Test

Q1. The maximum number of electrons in a sub shell is given by the expression
Answer : Option C
Explaination / Solution:

2(2l+1) = 4l+2

Q2. For d-electron, the orbital angular momentum is
Answer : Option D
Explaination / Solution:

Orbital angular momentum = √(l(l+1) h/2π

For d orbital = √(2 x 3) h/2π = √6 h/2π


Q3. What is the maximum numbers of electrons that can be associated with the following set of quantum numbers ? n = 3, l = 1 and m = –1
Answer : Option C
Explaination / Solution:

n = 3; l=1; m = -1

either 3px or 3py

i.e., Maximum two electrons can be accomodated either in 3px or in 3py


Q4.

Assertion : Number of radial and angular nodes for 3p orbital are 1, 1 respectively.

Reason : Number of radial and angular nodes depends only on principal quantum num-ber.
Answer : Option C
Explaination / Solution:

No. of radial node = n-l-1

No. of angular node = l

for 3p orbital

No. of angular node = l = 1

No. of radial node = n-l-1 = 3-1-1 = 1


Q5. The total number of orbitals associated with the principal quantum number n = 3 is
Answer : Option A
Explaination / Solution:

n = 3; l = 0; ml = 0 - one s orbital

n = 3; l = 1; ml = -1, 0, 1 - three p orbitals

n = 3; l = 2; ml = -2, -1, 0, 1, 2 - five d Orbitals

Overall nine orbitals are possible.


Q6. If n = 6, the correct sequence for filling of electrons will be,
Answer : Option A
Explaination / Solution:

n = 6

According Aufbau principle,

6s →4f →5d →6p

ns → (n-1)f →(n-2)d → np


Q7. Consider the following sets of quantum numbers :




Which of the following sets of quantum number is not possible ?
Answer : Option B
Explaination / Solution:

(ii) l can have the values from 0 to n-1

n=2; possible 'l' values are 0, 1 hence l = 2 is not possible.

(iv)for l=0; m=-1 not possible

(v)for n=3 l = 4 and m = 3 not possible


Q8. How many electrons in an atom with atomic number 105 can have (n + l) = 8 ?
Answer : Option B
Explaination / Solution:

n+l = 8


Electronic configuration of atom with atomic number 105 is [Rn] 5f14 6d3 7s2



Q9. Electron density in the yz plane of 3dx 2 −y2   orbital is
Answer : Option A
Explaination / Solution:

Option (a) - Zero (Refer to Figure 2.9)


Q10. If uncertainty in position and momentum are equal, then minimum uncertainty in velocity is
Answer : Option C
Explaination / Solution: