Quantum Mechanics

Question 1

1. Principal Quantum Number (n)

Answer 1

Principal Quantum Number (n): Describes the energy level of an electron (1, 2, 3…).

Question 2

Niels bohr

Answer 2

Explanation: Bohr proposed the concept of quantized energy levels for electrons in atoms.

Question 3

2. What is the maximum number of electrons that can occupy a p-orbital?
   • a) 2
   • b) 6
   • c) 10
   • d) 14

Answer 3

2. Answer: b) 6
   Explanation: A p-orbital can hold a maximum of 6 electrons (2 electrons per p sub-orbital, with 3 sub-orbitals: px, py, and pz).

Question 4

3. The principal quantum number (n) describes:
   a) the shape of the orbital.
   b) the orientation of the orbital in space.
   c) the size and energy level of the orbital.
   d) the spin of the electron.

Answer 4

3. Answer: c) the size and energy level of the orbital
   Explanation: The principal quantum number (n) represents the energy level and size of the orbital.

Question 5

4. Hund’s rule states that:
   • a) Electrons fill the lowest energy orbitals first.
   • b) No two electrons in an atom can have the same set of quantum numbers.
   • c) Electrons will fill orbitals singly before pairing.
   • d) Electrons fill orbitals in order of increasing energy.

Answer 5

4. Answer: c) Electrons will fill orbitals singly before pairing.
   Explanation: Hund’s rule states that electrons will occupy degenerate orbitals singly before pairing to minimize repulsion.

Question 6

5. How many total electrons can the d-subshell hold?
   • a) 2
   • b) 6
   • c) 10
   • d) 14

Answer 6

5. Answer: c) 10
   Explanation: The d-subshell has 5 orbitals, and each can hold 2 electrons, totaling 10 electrons.

Question 7

1. What is the primary quantum number (n) used to describe?
   • A) The shape of an orbital
   • B) The orientation of an orbital
   • C) The size and energy level of an orbital
   • D) The spin of an electron

Answer 7

1. C) The size and energy level of an orbital

Question 8

2. Which quantum number determines the shape of an electron’s orbital?
   • A) Principal quantum number (n)
   • B) Angular momentum quantum number (l)
   • C) Magnetic quantum number (mₗ)
   • D) Spin quantum number (mₛ)

Answer 8

2. B) Angular momentum quantum number (l)

Question 9

3. Who is credited with the development of the Uncertainty Principle?
   • A) Albert Einstein
   • B) Niels Bohr
   • C) Werner Heisenberg
   • D) Erwin Schrödinger

Answer 9

3. C) Werner Heisenberg

Question 10

4. The Pauli Exclusion Principle states that…
   • A) No two electrons in the same atom can have the same set of quantum numbers.
   • B) Electrons must occupy the lowest available energy level.
   • C) Electrons fill orbitals singly before pairing.
   • D) Electrons exist in both particle and wave forms.

Answer 10

4. A) No two electrons in the same atom can have the same set of quantum numbers.

Question 11

5. Which rule requires that electrons occupy the lowest energy orbitals first?
   • A) Hund’s Rule
   • B) Aufbau Principle
   • C) Pauli Exclusion Principle
   • D) Heisenberg Uncertainty Principle

Answer 11

5. B) Aufbau Principle

Question 12

6. What does the magnetic quantum number (mₗ) indicate?
   • A) The main energy level of an electron
   • B) The shape of the orbital
   • C) The orientation of the orbital in space
   • D) The spin of an electron

Answer 12

6. C) The orientation of the orbital in space

Question 13

7. According to Hund’s Rule, electrons will…
   • A) Pair up in orbitals before filling other orbitals
   • B) Fill each orbital singly before pairing
   • C) Only occupy orbitals with opposite spins
   • D) Not occupy higher energy levels if lower levels are filled

Answer 13

7. B) Fill each orbital singly before pairing

Question 14

8. The spin quantum number (mₛ) has possible values of…
   • A) 0, +1, -1
   • B) +1, -1
   • C) +1/2, -1/2
   • D) -1/2, 0, +1/2

Answer 14

8. C) +1/2, -1/2

Question 15

9. Which scientist is known for the wave equation describing electron behavior in atoms?
   • A) Niels Bohr
   • B) Albert Einstein
   • C) Werner Heisenberg
   • D) Erwin Schrödinger

Answer 15

9. D) Erwin Schrödinger

Question 16

10. What is the significance of the angular momentum quantum number (l)?
    • A) It determines the spin of an electron
    • B) It describes the shape of the orbital
    • C) It determines the main energy level of the electron
    • D) It describes the electron’s position

Answer 16

10. B) It describes the shape of the orbital

Question 17

11. What principle explains why no two electrons can have identical quantum numbers?
    • A) Aufbau Principle
    • B) Pauli Exclusion Principle
    • C) Hund’s Rule
    • D) Schrödinger’s Wave Equation

Answer 17

11. B) Pauli Exclusion Principle

Question 18

12. Who introduced the concept of quantized energy levels?
    • A) Niels Bohr
    • B) Albert Einstein
    • C) Werner Heisenberg
    • D) Max Planck

Answer 18

12. A) Niels Bohr

Question 19

13. According to the Heisenberg Uncertainty Principle, it is impossible to…
    • A) Determine both the position and energy of a particle at the same time
    • B) Determine both the position and momentum of a particle simultaneously with certainty
    • C) Determine the energy of a photon and its wavelength simultaneously
    • D) Predict the exact path of an electron in an atom

Answer 19

13. B) Determine both the position and momentum of a particle simultaneously with certainty

Question 20

14. In which orbital would you expect to find an electron with quantum numbers n=3 and l=2?
    • A) 3s
    • B) 3p
    • C) 3d
    • D) 3f

Answer 20

14. C) 3d

Question 21

15. What is the maximum number of electrons that can occupy a single orbital?
    • A) 1
    • B) 2
    • C) 4
    • D) 6

Answer 21

15. B) 2