Chemistry Test Atomic Structure 3 — Questions and Answers
Question 1: The photoelectric effect provided evidence that light behaves as:
- A continuous wave
- A stream of particles called photons (Correct answer)
- A magnetic field
- A standing wave
Correct answer: A stream of particles called photons
Einstein explained the photoelectric effect by proposing that light consists of discrete packets of energy called photons.
Question 2: Which element has the electron configuration [Ne] 3s² 3p⁶ 3d⁵ 4s²?
- Iron (Fe)
- Manganese (Mn) (Correct answer)
- Chromium (Cr)
- Zinc (Zn)
Correct answer: Manganese (Mn)
Manganese (Mn, Z=25) has the configuration [Ar]3d⁵4s², which written without the argon abbreviation matches [Ne]3s²3p⁶3d⁵4s².
Question 3: According to Heisenberg's Uncertainty Principle, it is impossible to simultaneously know precisely the electron's:
- Charge and mass
- Position and momentum (Correct answer)
- Spin and charge
- Mass and energy
Correct answer: Position and momentum
Heisenberg's Uncertainty Principle states that the more precisely position is known, the less precisely momentum (and therefore velocity) can be known.
Question 4: Which of the following ions is isoelectronic with the noble gas neon (Ne)?
- Na⁺ (Correct answer)
- K⁺
- Ca²⁺
- Mg²⁺
Correct answer: Na⁺
Na⁺ loses one electron from its 11-electron neutral state, giving it 10 electrons — the same as neon.
Question 5: Which property of electrons was demonstrated by the Davisson-Germer experiment?
- Wave-particle duality (Correct answer)
- Negative charge
- Constant spin
- Orbital quantization
Correct answer: Wave-particle duality
The Davisson-Germer experiment showed electron diffraction, proving electrons have wave-like properties (wave-particle duality).
Question 6: In the ground state, which orbital does the 25th electron of manganese occupy according to Hund's rule?
- 3d with paired spin
- 4s with paired spin
- 3d with unpaired spin (fifth 3d electron) (Correct answer)
- 4p
Correct answer: 3d with unpaired spin (fifth 3d electron)
Manganese's configuration is [Ar]3d⁵4s²; the 3d subshell receives one electron per orbital before pairing, so the 5th 3d electron is unpaired.
Question 7: The de Broglie wavelength of a particle is inversely proportional to its:
- Temperature
- Charge
- Momentum (Correct answer)
- Volume
Correct answer: Momentum
De Broglie's equation λ = h/p shows wavelength is inversely proportional to momentum (mass × velocity).
Chemistry Test Atomic Structure 3
The photoelectric effect provided evidence that light behaves as: