KCL Section 6: Atomic line spectra (Waves and photons)

Question 1

Do standing waves store or transfer energy

Answer 1

Store

Question 2

In free atoms, the locations that electrons can be in around the nucleus are _______, and have ________ (‘________’) values.

Answer 2

In free atoms, the locations that electrons can be in around the nucleus are specific, and have exact (‘quantised’) values.

Question 3

True or False

Electrons can be found at any of these levels, but it takes less energy to be at a higher level

Answer 3

False

Question 4

How many possible different levels can an electron be at in an atom

Answer 4

The amount of energy levels are technically infinite but they get closer and closer together

Question 5

Explain why electrons require energy to move to a higher energy level.

Answer 5

Electrons are negative
Electrons are attracted to the positive nucleus of an atom
Moving further away from the nucleus requires work to be done against the attractive force
Energy is required in order for the electrons to do work

Question 6

Explain why the three electron transitions shown absorb different colours of light

Answer 6

An electron moving to a higher energy level does work against the attraction from the nucleus
The larger the difference in energy, the more work the electron must do
An electron requires more energy to do more work
E = hf
If more energy is required by the electron, a higher frequency of light must be absorbed

Question 7

Which model of light (wave or photon) is supported by absorption spectra?

Observations:

• Discrete wavelengths of light are absorbed
• The wavelengths absorbed are always the same value for a particular element
• The wavelengths correspond to the size of the gap between energy levels
• Other wavelengths are not absorbed

Answer 7

The photon model should be used

Question 8

If white light is shone through an element which has the energy levels shown, what would an observer see?

Answer 8

White light contains all frequencies / wavelengths of visible light
Three specific frequencies / wavelengths would be absorbed
The observer would see all of the remaining frequencies / wavelengths without those three

Question 9

True or false

Light photons hit the electrons and transfer energy

Answer 9

Light photons hit the electrons and transfer energy (TRUE)

Question 10

What happens if too much or too little energy is transmitted to an electron

Answer 10

A specific amount of energy is needed to cause an electron to move otherwise energy will be remitted and the electron will fall back to it’s original shell.

Question 11

If a spectrum of light is used to illuminate the sample, the ______ which _____ the gaps between the energy levels will be ________: the view from the other side of the sample is the ______ ___________:

Answer 11

If a spectrum of light is used to illuminate the sample, the photons which match the gaps between the energy levels will be absorbed: the view from the other side of the sample is the absorption spectra:

Question 12

How can you use light to find out which levels electrons are at?

Answer 12

Red light is for the first levels and blue for the last few