Atoms

Q1.When an electron in a hydrogen atom transitions from a higher energy level to a lower energy level, it:

• AAbsorbs a photon
• BEmits a photon
• CEmits an electron
• DAbsorbs a proton

Q2.A difference of 2.3 eV separates two energy levels in an atom. What is the frequency of radiation emitted during the transition? (h = 6.63×10⁻³⁴ J·s)

• A5.55 × 10¹⁴ Hz
• B5.55 × 10¹¹ Hz
• C2.77 × 10¹⁴ Hz
• D1.11 × 10¹⁵ Hz

Q3.In Bohr's model of hydrogen, the total energy Eₙ = –13.6/n² eV. The ratio E₃/E₁ is:

• A9
• B1/9
• C3
• D1/3

Q4.According to classical electromagnetic theory, an electron orbiting the nucleus should emit radiation of frequency equal to its orbital frequency (≈ 6.6×10¹⁵ Hz for n=1 Bohr orbit). Why is this problematic?

• AThe frequency is too high to be observed
• BThe electron would lose energy, change its frequency, and emit a continuous spectrum — collapsing into nucleus
• CX-rays cannot be emitted from hydrogen
• DThe proton would absorb the radiation

Q5.In Bohr's model, if the radius of the first orbit (n=1) is a₀ = 0.53 Å, what is the radius of the second orbit (n=2)?

• A1.06 Å
• B2.12 Å
• C0.265 Å
• D4.24 Å