This set of Physical Chemistry Multiple Choice Questions & Answers (MCQs) focuses on “Atomic Term Symbols”.
1. Who discovered the Balmer formula for a series of hydrogen emission lines?
a) Russell-Saunders
b) Johannes Rydberg
c) Johann Balmer
d) Walter Ritz
View Answer
Explanation: In 1885, Johann Balmer, a Swiss mathematician, discovered the Balmer formula for a series of hydrogen emission lines. Later, some changes were done by Johannes Rydberg and Walter Ritz in the formula whereas Russell-Saunders is also known as L-S coupling.
2. Which form represents term symbols in the Russell-Saunders coupling?
a) 2S+1L2
b) 2L+1SJ
c) 2S+1LJ
d) 2S+1J
View Answer
Explanation: In Russell-Saunders coupling, term symbols are represented by 2S+1LJ form, where S represents the total spin angular momentum, L represents the total orbital angular momentum and J refers to the total angular momentum.
3. How many quantum numbers describe the spherically symmetric potential field of an electron?
a) One
b) Two
c) Three
d) Four
View Answer
Explanation: Because of the different energies and other properties of electron orbitals, electron in a spherically symmetric potential field can be described by four quantum numbers all together, which applies to hydrogen-like atoms only.
4. Which phenomenon is used to describe the position of an electron around the nucleus?
a) Angular Momentum
b) Spin angular momentum
c) Orbital angular momentum
d) Azimuthal angular momentum
View Answer
Explanation: The term angular momentum describes the phenomenon that an electron distributes its position around the nucleus. The angular momentum of an electron orbiting around the nucleus is quantized.
5. Is the following table true or false?
| NUMBER | SYMBOL |
|---|---|
| Principal Quantum Number | l |
| Azimuthal Quantum Number | n |
| Magnetic Quantum Number | ms |
| Spin Quantum Number | ml |
a) True
b) False
View Answer
Explanation: Correct order of quantum numbers with their symbols and possible values is given below;
| NUMBER | SYMBOL | POSSIBLE VALUES |
|---|---|---|
| Principal Quantum Number | l | 1, 2, 3, 4,….. |
| Azimuthal Quantum Number | n | 0, 1, 2, 3,……,(n-1) |
| Magnetic Quantum Number | ms | -l,……, -1, 0, 1, ……,l |
| Spin Quantum Number | ml | +1/2, -1/2 |
6. How many angular nodes an atom has, when the value of l is 4?
a) 2
b) 1
c) 5
d) 4
View Answer
Explanation: Given, l = 4
Angular node is a region where the angular wave function is zero.
Since, the number of angular modes is equal to the value of l
Therefore, the number of nodes is also 4.
7. Which orbital quantum number is used to represent the azimuthal angular momentum?
a) n
b) l
c) ml
d) ms
View Answer
Explanation: The orbital quantum number, l is used to represent the azimuthal angular momentum. Its range vary from 0 to n-1, where n is principal quantum number. The possible values for l range from 0,1,2,3……,(n-1).
8. Which of the following phenomena explains the inherent magnetic momentum?
a) Azimuthal angular momentum
b) Intrinsic angular momentum
c) Spin angular momentum
d) Orbital angular momentum
View Answer
Explanation: The intrinsic angular momentum of a particle explains its inherent magnetic momentum. The intrinsic angular momentum of an electron is called its spin. The intrinsic energy includes the self-field energy of the particle as well as the energy of the internal workings of the particle.
9. Who proposed the LS coupling first?
a) Johann Balmer
b) Henry Russell
c) Frederick Saunders
d) Henry Russell and Frederick Saunders
View Answer
Explanation: LS coupling was first proposed in 1923 by Henry Russell and Frederick Saunders. It exactly explained the fine structures of hydrogen-like atomic spectra. It is also known by the name Russell-Saunders coupling scheme.
10. Which of the following statements are true?
Statement 1: LS coupling is suitable for lighter atoms.
Statement 2: JJ coupling is suitable for heavier atoms.
a) Statement 1 is true but statement 2 is false
b) Statement 2 is true but statement 1 is false
c) Statement 1 and statement 2, both are true
d) Statement 1 and statement 2, both are false
View Answer
Explanation: In LS coupling S, L, J and MJ are four quantum numbers used to describe electronic states in lighter atoms. JJ coupling is more applicable in heavier atoms, where the four quantum numbers are J, MJ, ML and MS.
Sanfoundry Global Education & Learning Series – Physical Chemistry.
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