Selected MCQ

Current Question
Which quantum number determines orbital shape?
  • A. Principal
  • B. Azimuthal
  • C. Magnetic
  • D. Spin
Correct Answer: B
Explanation:
Azimuthal quantum number defines orbital geometry.
Related Question 1
Which quantum number set is impossible for an electron in an atom?
  • A. (n=3,\ l=2,\ m_l=1)
  • B. (n=2,\ l=2,\ m_l=0)
  • C. (n=4,\ l=1,\ m_l=-1)
  • D. (n=1,\ l=0,\ m_l=0)
Correct Answer: B
Explanation:
For principal quantum number (n), the azimuthal quantum number must satisfy (0 \le l \le n-1).
Related Question 2
In molecular orbital theory, antibonding orbitals have:
  • A. Lower energy
  • B. Higher energy
  • C. Same energy
  • D. Zero energy
Correct Answer: B
Explanation:
Antibonding orbitals destabilize molecule.
Related Question 3
In a Hilbert space formulation of quantum mechanics, physical states are represented by:
  • A. Real numbers
  • B. Vectors up to a global phase
  • C. Scalars only
  • D. Matrices only
Correct Answer: B
Explanation:
States are rays in Hilbert space, invariant under global phase.
Related Question 4
In quantum mechanics, the commutator ([x,p]) equals:
  • A. 0
  • B. (i\hbar)
  • C. (-i\hbar)
  • D. (\hbar^2)
Correct Answer: B
Explanation:
Position and momentum operators satisfy ([x,p]=i\hbar).
Related Question 5
In quantum mechanics, expectation value of an observable corresponds to:
  • A. Most probable value
  • B. Average measurement over many identical systems
  • C. Minimum energy
  • D. Maximum probability
Correct Answer: B
Explanation:
Expectation value is statistical mean of repeated measurements.