Unit 4 - Electron Structure

Which scientist proposed that electrons orbit the nucleus in specific energy levels?

• Bohr
• Rutherford
• Thomson
• Dalton

Answer explanation

Bohr introduced quantized electron orbits explaining line spectra

What happens when an electron drops from a higher energy level to a lower one?

• It emits a photon
• It absorbs a photon
• It ionizes
• It gains mass

Answer explanation

Energy is released as a photon during a drop to a lower level

Which element emits a red spectral line in a flame test?

• Sodium
• Calcium
• Strontium
• Copper

Answer explanation

Strontium gives off a red emission when excited

What equation represents the energy of emitted photons?

Answer explanation

Planck's equation relates energy to frequency

Line spectra are unique to each element because...

• Each has different energy level spacing
• They all absorb the same energy
• They contain different protons
• Electrons orbit randomly

Answer explanation

The energy difference between levels is unique to each atom

Which region of the EM spectrum corresponds to visible light?

• Infrared
• Ultraviolet
• Microwave
• 400–700 nm

Answer explanation

Visible light spans from ~400–700 nanometers in wavelength

In a hydrogen spectrum, what causes the Balmer series lines?

• Transitions to n=1
• Transitions to n=2
• Transitions to n=3
• Ionization

Answer explanation

Balmer lines are from higher levels falling to n=2

Bohr's model explains why only certain energy transitions occur. This is evidence for...

• Continuous energy
• Randomness in atoms
• Quantized energy levels
• Atomic weight variation

Answer explanation

Energy levels are fixed and discrete → quantization

Which color in visible light has the highest energy?

• Red
• Green
• Violet
• Orange

Answer explanation

Shorter wavelength (violet) = higher energy

Bohr's model fails to explain the spectra of...

• Hydrogen
• Helium
• Sodium
• All atoms

Answer explanation

It only accurately describes hydrogen’s single electron