science beginner 10 sample questions

Atomic Structure MCQ Practice Test

Fundamental particles and arrangements

Q1. Considering the relativistic effects on the electron orbitals of a heavy atom like Uranium (U), which of the following statements most accurately describes the impact on the 6s and 6p orbitals' energy levels relative to their non-relativistic counterparts?

A. The 6s orbital experiences a greater energy decrease than the 6p orbital due to its higher probability density near the nucleus. ✓
B. The 6p orbital experiences a greater energy decrease than the 6s orbital due to its higher angular momentum.
C. Both 6s and 6p orbitals experience a similar energy decrease due to relativistic effects being primarily dependent on the principal quantum number.
D. Relativistic effects have a negligible impact on the energy levels of the 6s and 6p orbitals in Uranium.

Explanation: Relativistic effects become significant in heavy atoms due to the high speed of electrons close to the nucleus. The 6s orbital, having a higher probability density near the nucleus compared to the 6p orbital, experiences stronger relativistic contraction. This contraction leads to a greater decrease in energy for the 6s orbital compared to the 6p orbital.

Q2. Which of the following statements accurately describes the relationship between the orbital angular momentum (L) and the orbital magnetic dipole moment (μ_L) for an electron in a hydrogen atom?

A. μ_L = (e / 2m) * L ✓
B. L = (e / 2m) * μ_L
C. μ_L = (e / m) * L
D. L = (e / m) * μ_L

Explanation: The orbital magnetic dipole moment (μ_L) is related to the orbital angular momentum (L) by the equation μ_L = (e / 2m) * L, where e is the elementary charge and m is the mass of the electron. This relationship arises from the electron's charge and its motion around the nucleus. The Bohr magneton is often used to express this relationship, but the core relationship is between the charge, mass and angular momentum.

Q3. Which of the following orbitals in a hydrogen atom has a nodal plane that passes through the nucleus?

A. s-orbital with a nodal plane at r = 0
B. p-orbital with a nodal plane at π = π/2 ✓
C. d-orbital with a nodal plane at r = 0
D. p-orbital with a nodal plane at r = 0

Explanation: In a hydrogen atom, the p-orbital has a nodal plane that passes through the nucleus, which is perpendicular to the axis of the orbital. This is because the p-orbital has a nodal plane at π = π/2, which means that the probability of finding an electron at the nucleus is zero.

Q4. The energy level that is not completely filled with electrons in a xenon atom is the \u200b\u200b\u202f\u200b\u200boutermost energy level, which is the \u200b\u200b\u202f\u200b\u200b5p orbital. Which of the following energy levels is completely filled in a xenon atom?

A. The 5s orbital
B. The 4d orbital ✓
C. The 4f orbital
D. The 5p orbital

Explanation: In a xenon atom, the 5p orbital is the outermost energy level and is not completely filled. The 4d orbital is completely filled with 10 electrons.

Q5. When an electron transitions from the 3p orbital to the 3s orbital in a hydrogen atom, what is the change in the orbital angular momentum?

A. 0 ± ± 0 ✓
B. 1 ± ± 0
C. -1 ± ± 0
D. 0

Explanation: The orbital angular momentum is determined by the orbital angular momentum quantum number (l). For the 3s orbital, l = 0, and for the 3p orbital, l = 1. Therefore, the change in orbital angular momentum is 0 ± ± 0.

Q6. Which of the following orbitals in a multi-electron atom has the highest probability density at the nucleus?

A. s-orbital with n = 2 and l = 0 ✓
B. p-orbital with n = 3 and l = 1
C. d-orbital with n = 4 and l = 2
D. f-orbital with n = 5 and l = 3

Explanation: In a multi-electron atom, s-orbitals (l=0) have the highest probability density at the nucleus. The probability density at the nucleus decreases as the principal quantum number (n) increases for s orbitals. Therefore, the s-orbital with n = 2 has the highest probability density at the nucleus among the given options.

Q7. Which of the following subshells can hold a maximum of 2 electrons?

A. 4f subshell
B. 5d subshell
C. 6s subshell ✓
D. 3p subshell

Explanation: The 6s subshell can hold a maximum of 2 electrons because it has one orbital. The 4f subshell can hold a maximum of 14 electrons, the 5d subshell can hold a maximum of 10 electrons, and the 3p subshell can hold a maximum of 6 electrons.

Q8. Which of the following orbitals in a hydrogen atom has the highest probability of finding an electron at a distance of 3.00 Å from the nucleus?

A. 2p orbital ✓
B. 3d orbital
C. 4f orbital
D. 6g orbital

Explanation: The 2p orbital has its highest probability density between 1.5 and 2.0 Å from the nucleus, making it more likely to find an electron at a distance of 3.00 Å from the nucleus compared to other orbitals.

Q9. Which of the following orbitals in a hydrogen atom has the same energy level as the 2s orbital?

A. 2s orbital
B. 2p orbital ✓
C. 3s orbital
D. 4s orbital

Explanation: In a hydrogen atom, the energy of an orbital depends only on the principal quantum number (n). Orbitals with the same 'n' value have the same energy. The 2s and 2p orbitals both have a principal quantum number of 2, and therefore have the same energy.

Q10. When an electron transitions from the 2p orbital to the 2s orbital in a hydrogen atom, what is the change in the electron's orbital angular momentum?

A. an increase in orbital angular momentum by ħ
B. a decrease in orbital angular momentum by ħ ✓
C. no change in orbital angular momentum
D. a decrease in orbital angular momentum by 2ħ

Explanation: The orbital angular momentum of an electron is determined by the orbital angular momentum quantum number (l). The orbital angular momentum is given by sqrt(l(l+1))ħ. When an electron transitions from the 2p orbital (l = 1) to the 2s orbital (l = 0), its orbital angular momentum decreases. The magnitude of the decrease is determined by the difference in the orbital angular momentum quantum number, which is 1 (2p to 2s). Therefore, the orbital angular momentum decreases by ħ.

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