DAT General Chemistry: Atomic Structure and Periodic Trends 2 — Questions and Answers
Question 1: What is the correct ground-state electron configuration of copper (Z = 29)?
- [Ar]3d⁹4s²
- [Ar]3d¹⁰4s¹ (Correct answer)
- [Ar]3d⁸4s²
- [Ar]3d¹⁰4s²
Correct answer: [Ar]3d¹⁰4s¹
Copper is an exception to the Aufbau principle; it adopts [Ar]3d¹⁰4s¹ because a fully filled 3d subshell provides extra stability.
Question 2: Which equation correctly gives the energy of a photon?
- E = mc²
- E = hν (Correct answer)
- E = ½mv²
- E = kq₁q₂/r²
Correct answer: E = hν
Planck's equation E = hν states that photon energy equals Planck's constant (h) multiplied by the photon's frequency (ν).
Question 3: The de Broglie hypothesis proposes that:
- Only photons exhibit wave-particle duality
- All matter exhibits wave-like properties with wavelength λ = h/mv (Correct answer)
- Electrons are stationary particles orbiting the nucleus
- Energy and matter are interchangeable forms of the same entity
Correct answer: All matter exhibits wave-like properties with wavelength λ = h/mv
de Broglie proposed that all matter has an associated wavelength λ = h/mv, extending wave-particle duality beyond photons to all particles.
Question 4: Hund's rule states that electrons in degenerate orbitals will:
- Pair up in the same orbital before occupying empty orbitals
- Occupy separate orbitals with parallel spins before any pairing (Correct answer)
- Always have opposite spins regardless of orbital occupancy
- Fill the lowest-energy orbital completely before entering the next
Correct answer: Occupy separate orbitals with parallel spins before any pairing
Hund's rule states that electrons fill degenerate orbitals singly with parallel spins before any orbital receives a second electron.
Question 5: Which property generally INCREASES as you move down a group in the periodic table?
- Electronegativity
- First ionization energy
- Atomic radius (Correct answer)
- Electron affinity
Correct answer: Atomic radius
Atomic radius increases down a group because each successive element gains an additional electron shell, increasing the distance between the nucleus and valence electrons.
Question 6: The Heisenberg Uncertainty Principle states that:
- The exact position and exact momentum of a particle cannot both be precisely known simultaneously (Correct answer)
- Electrons always occupy the lowest available energy level
- No two electrons in an atom can share all four quantum numbers
- Atomic orbitals are regions of zero electron probability
Correct answer: The exact position and exact momentum of a particle cannot both be precisely known simultaneously
Heisenberg's Uncertainty Principle mathematically limits how precisely both position and momentum of a particle can be simultaneously determined (Δx · Δp ≥ ℏ/2).
Question 7: Among the elements Li, Be, B, and Ne, which has the highest first ionization energy?
- Li
- Be
- B
- Ne (Correct answer)
Correct answer: Ne
Noble gases have the highest ionization energies in their periods because their completely filled valence shells are exceptionally stable and strongly resist electron removal.
DAT General Chemistry: Atomic Structure and Periodic Trends 2
What is the correct ground-state electron configuration of copper (Z = 29)?