1. The uncertainty in the position of an electron \[\left(mass=9.1 × 10^{-28}g\right)\] moving with a velocity of \[3.0 × 10^{4}cms^{-1}\] accurate upto 0.011% will be

a) 1.92 cm

b) 7.68 cm

c) 0.175 cm

d) 3.84 cm.

Explanation:

2. The uncertainty in the momentum of an electron is \[1.0 × 10^{-5}kg ms^{-1}\] . The uncertainty in its position will be \[\left(h = 6.62 × 10^{-34}kg m^{2}s^{-1}\right)\]

a) \[1.05 × 10^{-26}m \]

b) \[1.05 × 10^{-28}m \]

c) \[5.27 × 10^{-30}m \]

d) \[5.25 × 10^{-28}m \]

Explanation:

3. Azimuthal quantum number determines the

a) size

b) spin

c) orientation

d) angular momentum of orbitals

Explanation:

4. When the value of azimuthal quantum number, l = 2, value of ‘n’ will be

a) 3

b) 4

c) 5

d) any one of these

Explanation: For l = 2 (d subshell) n \[\geq\] 3

5. The values of quantum numbers n, l and m for the 5^{th} electron of Boron will be

a) n = 1, l = 0, m = –1

b) n = 2, l = 1, m = –1

c) n = 2, l = 2, m = –1

d) n = 1, l = 2, m = –1

Explanation:

6. The total number of orbitals in a shell with principal quantum
number ‘n’ is

a) 2n

b) \[2n^{2}\]

c) \[n^{2}\]

d) n

Explanation: Number of orbitals with principal quantum number n = n

^{2}

7. Which one of the following set of quantum numbers is not possible for 4p electron?

a) \[n = 4, l = 1, m = –1,m_{s}=+\frac{1}{2}\]

b) \[n = 4, l = 1, m = 0,m_{s}=+\frac{1}{2}\]

c) \[n = 4, l = 1, m = 2,m_{s}=+\frac{1}{2}\]

d) \[n = 4, l = 1, m = –1,m_{s}=-\frac{1}{2}\]

Explanation: For 4p electron n = 4, l = 1, m = –1, 0 + 1 and s = +½ or –½

8. The maximum number of electrons in subshell with l = 2 and n = 3 is

a) 2

b) 6

c) 12

d) 10

Explanation: l = 2 for d subshell hence 10 electrons

9. An electron has principal quantum number 3. The number of its (i) sub-shells and (ii) orbitals would be respectively

a) 3 and 5

b) 3 and 7

c) 3 and 9

d) 2 and 5

Explanation: When n = 3 we have s,p and d sub-shells. Hence subshells = 3 and obitals 1 + 3 + 5 = 9

10. An \[\overline{e}\] has magnetic quantum number as –3, what is its principal quantum number

a) 1

b) 2

c) 3

d) 4

Explanation: When m = – 3, l = 3

n = 4