Atom Energy Levels

Question 1

What are electrons in an atom trapped by?

Answer 1

Electrostatic force of attraction of the nucleus.

Question 2

How do the different energies compare between electrons close to the atom, and those far from it?

Answer 2

Electrons in a shell near the nucleus has less energy than an electron in a shell further away from the nucleus.

Question 3

What is the ground state?

Answer 3

The lowest energy stage of an atom.

Question 4

What happens when an atom in the ground state absorbs energy?

Answer 4

One of its electrons moves to a shell at a higher energy, the atom is now in an excited state.

Question 5

What units are used?

Answer 5

Electron Volts, eV.

Question 6

What is the electron volt defined as?

Answer 6

• The kinetic energy carried by an electron after it has been accelerated through a potential difference of 1 volt.
• Energy gained by electron = Acceleration Voltage
• 1 eV = 1.60 x 10^-19 J

Question 7

Why is the electron configuration in an excited atom unstable?

Answer 7

•Electron that moves to an outer shell leaves a vacancy in the shell it moves from.

Question 8

How do atoms move a lower energy level?

Answer 8

Process called de-excitation:

• Electrons move down energy levels by emitted a photon.

Question 9

What is the energy of the emitted photon?

Answer 9

• Energy of the photon is equal to the energy lost by the electron and therefore by the atom.
• Energy of the emitted photon, hf = E1 - E2
Moves from energy level E1 to a lower energy level E2

Question 10

What is the required energy for the excitation of photons?

Answer 10

• An electron in an atom can absorb a photon and move to an outer shell where a vacancy exists.
• This can only occur if the energy of the photon is exactly equal to the difference between the final and initial energy levels of the atom
• Energy of the photon must be exactly equal to the gain in electron’s energy

Question 11

What is the formula of the energy carried by each photon/change in energy?

Answer 11

ΔE = E2 - E1 = hf = hc`/λ

Question 12

What is excitation?

Answer 12

The movement of an electron to a higher energy level.

Question 13

What is a fluorescent tube?

Answer 13

• Glass tube with a fluorescent coating on its inner surface.
• Tube contain mercury vapor at low pressure.

Question 14

Why does the fluorescent tube emit visible light?

Answer 14

• Ionization and excitation of the mercury atoms occur as they collide with each and with electrons in the tube.
• Mercury atoms emit ultraviolet photons, as well as visible photons and photons of much less energy when they de-excite.
• Ultraviolet photons are absorbed by the atoms of the fluorescent coating, causing excitation of the atoms.
• Coating atoms de-excite in steps and emit visible photon
• Phosphorus coating on the inside of the tube absorbs these photons, exciting its electrons to much higher orbits, these electrons then cascade down the energy levels, emitted lower energy photons int he form of visible light.