Emission Spectra

Question 1

Describe Max Planck’s theory.

Answer 1

Planck ignored 4000 years of prior understanding.

He made a leap of faith saying that the energy released from hot objects can only be released in small packets or bundles called photons.

He said that the energy is quantised – in specific, small amounts.

Question 2

What does light travel in?

Answer 2

They travel in photons.

Question 3

What does each photon have?

Answer 3

Each photon has it’s own ‘discrete’ energy value which depends upon it’s frequency.

Question 4

What is the equation for Max Planck’s theory?

Answer 4

E = hf (h x f)

E = Energy (J)
F = Frequency (Hz)
h is Planck’s constant
h = 6.63x10-34Js

Question 5

State what energy levels consist of and where are they located?

Answer 5

They consist of electrons

They exist in shells around the nucleus.

Question 6

How many electrons on each shell?

Answer 6

First shell = 2
Second Shell = 8
Third Shell = 8

Question 7

What is the first shell called?

Answer 7

The ground state.

Question 8

What are the other shells called?

Answer 8

Excited levels

Question 9

In what type of energy level can electrons only exist in?

Answer 9

Electrons can only exist in discrete energy levels.

Question 10

How does the location of electrons link with the energy being produced?

Answer 10

The closer the electrons are to the nucleus, the less amount of energy being produced.

The further away the electrons are to the nucleus, the more amount of energy being produced.

Question 11

What happens if an electron gains extra energy?

Answer 11

If an electron gets some extra energy (and this can happen by two methods…) it can jump up to the next energy level and we say it is in an EXCITED STATE!

Question 12

Describe the process of excitation.

Answer 12

If the electrons gain enough energy they will get really excited. If they get excited enough they will jump to the next level.

The amount of energy they need to jump an energy level is a quantised amount, it is different for every energy level and every different atom.

If they don’t get the EXACT amount, they won’t jump (so they need particular frequencies)

It can happen two ways.

Question 13

Describe the process of excitation by electron collision.

Answer 13

An electron that is moving will have a particular kinetic energy.

If this energy is the ‘right’ amount and it collides with an electron in an atom, it can transfer this kinetic energy.

Question 14

Describe the process of excitation by photon absorption.

Answer 14

An electron can also jump to a higher energy level (if there is a gap) by absorbing a photon.

Again, the energy must be exact.

If the energy is high enough, it might even be able to jump two energy levels.

Question 15

Describe what happens for De-excitation?

Answer 15

Electrons cannot stay in an excited state for very long. They like to be in the lowest possible energy level (the ground state) and they will go there if they are left alone.

Each time an electron falls to a lower energy level it loses energy. This energy is radiated as a photon of frequency ‘f’.

Question 16

What is the equation that links with excitation and de-excitation?

Answer 16

E1 – E2 = ΔE = hf

Find the difference between two energy levels and this will result the difference of energy. This equals the frequency (f) and planck’s constant (h)

E = Energy (J) 
h = Planck's constant (Js) (h = 6.63x10-34Js)
f = Frequency (Hz)

Question 17

What happens if an electron falls down to a lower energy level?

Answer 17

Every time the electron falls back down to a lower energy level, the energy that it ‘loses’ is emitted as a photon.

Each energy level jump will produce a single photon.

So an electron falling from the 2nd state back to the ground state will emit two separate photons, each with different energies (as the amount of energy between each level is different).

Question 18

What is the link between the emission spectrum and electrons falling down a lower energy level?

Answer 18

If the electrons jump down an energy level, they only emit photon’s of certain energy - hence frequencies - which can be shown on an emission spectrum.

Question 19

State the colours in the hydrogen spectrum and state the number of each colour.

Answer 19

Red = 656.2 nm
Green = 486.1 nm
Violet = 434.0 nm 
Indigo = 410.1 nm

Question 20

Describe the diagram used to identify gases using the hydrogen spectrum.

Answer 20

Firstly, Gas discharged tube containing hydrogen.
Secondly, There are 2 slits placed in front of the tube.
Thirdly, There is clear prism placed in front of the 2 slits.
Finally, it produces different colour light which identifies gases.

To identify what colour the light is producing remember the numbers that have been stated for the hydrogen spectrum and this will identify what colour light is producing.