1. Electrons & Energy Levels

2. The Atom Electrons are held at set distances from
the nucleus in what we call shells

3. What keeps the
electrons and shells
spaced apart?

4. Energy levels in the electrons
The energy
held by an
electron
determines
the orbital
shell the
electron will
occupy

5. Increasing Energy Levels
Highest
energy
level
Lowest
energy
level

6. Packets of energy
The best way to visualise the energy levels in electron
orbits is to use the packet diagram.
You can see the different energy
levels of the electron orbits.
They are like flight of stairs

7. Totally False So what we know The nucleus is a fixed ball
of protons and neutrons
in the centre of the atom.
The electrons exist in a fixed
shell around the nucleus, and
stay in the shell due to their
energy levels.
Totally False

8. So it’s false, can you work out the truth
The ______ of an atom consists of _______ and neutrons in the ____. They are constantly _______ round like footballs, this spinning action causes them to ____ and ____ over each other all of the time.
The _______ exist in a fixed _____ around the nucleus, their position depends on the _____ level of the electron. They are constantly spinning around the nucleus in their _____, like planets around the sun. They can jump to a new higher ____ with an injection of energy and when they ___ energy they will drop into a lower shell.
slip, shell, nucleus, shell, lose, slide, protons, orbits,
constantly, energy, spinning, centre, electrons, lower

9. So it’s false, can you work out the truth
The nucleus of an atom consists of protons and neutrons in the centre. They are constantly spinning round like footballs, this spinning action causes them to slip and slide over each other all of the time.
The electrons exist in a fixed shell around the nucleus, their position depends on the energy level of the electron. They are constantly spinning around the nucleus in their orbits, like planets around the sun. They can jump to a new higher shell with an injection of energy and when they lose energy they will drop into a lower shell.

10. So how can an electron jump from one energy level to another
What will it need to make the jump

11. So how can an electron jump from one energy level to another
What will it need to make the jump
To go to a higher energy level it needs an input of energy
It drops down again as it loses the energy it gained.

12. An electromagnetic wave like light hits the electron:
The energy it is carrying
is passed to the electron
this excites the electron
and it jumps to a higher orbit

13. This input of high energy gives the electron so much energy it causes
Gamma wave
lots of
energy
This input of high energy
gives the electron so
much energy it causes
the electron to jump
completely off the atom

14. So with the
electron gone.
What will this mean
to the overall charge
on the atom?

15. This is Ionisation 1 more proton than electrons means that
the atom now has an
an overall charge of +1
The atom has been
changed into a
charged Ion
This is Ionisation

16. So how do we know this?
Sunday, 17 February 2019

17. The electron
Thompson was studying the conductivity of gases in fluorescent tubes (neon) when he discovered the electron.
An electric current flows through a low pressure gas when a high potential difference is applied between two electrodes
The Cathode (negative electrode) gave off some invisible rays (Cathode rays)
These rays could be deflected by electric fields  they were negatively charged particles called ELECTRONS.
Low pressure gas
Cathode
Anode

18. Thermionic emission
It is possible to produce electron emission from metals using low voltage between the anode and the cathode.
The cathode has to be heated up to high temperatures (by a current flowing through a filament)
Electrons will escape from the filament (Cathode)
Electrons
Cathode

19. Thermionic emission
What would happen to the electrons if an anode (positive electrode) is placed near the cathode?
The emitted electrons are attracted by the anode
The anode exerts a force on each electron  the electrons gain K.E.
Vacuum
Cathode
Anode

20. Electron deflection
So, how did Thompson realised that the “cathode rays” are streams of negative particles?
The cathode rays could be deflected by electric, or magnetic fields.
Electrodes
Draw the path of the electrons that go through the hole in the anode and between the positive and negative electrodes.
Cathode
Anode

21. Electron-volt
We can measure the Ek (Kinetic Energy) of a charge which is accelerated across a potential difference using this formula:
Kinetic Energy (J) = Charge (C) x Voltage (V)
The charge of the electron (elementary charge) is e = 1.60 x C
So, we can define a new unit of energy, the ELECTRONVOLT:
One electronvolt is the Kinetic Energy gained by an electron when it is accelerated through a potential difference of one volt.

22. Energy Levels

23. Neon Lamps
But, why do fluorescent tubes emit light of different… C O L O U R S
The gas that fills the tubes is different, so it emits different colour light when an electric current flows through it.
And why do different gases emit different colours?
To answer this question we must understand the nature of light and electromagnetic radiation, and the structure of the atom.

24. Neon Lamps
Shine the light from a light bulb and different gas lamps through a prism. Then look at the spectra. What do you notice? What is the difference between the spectrum from the light bulb and the gas lamps?
The light bulb gives a Continuous Spectrum.
The gas lamps give a Line Spectrum.
Each gas lamp gives different lines in their spectrum.
Continuous Spectrum
Line Spectrum

25. The Hydrogen Spectrum
All elements have their own line spectrum emitted when an electric charge is passed through their vapour. For an hydrogen discharge tube this is the line spectrum we would obtain:
410 nm
434 nm
486 nm
656 nm
500 nm
600 nm
700 nm
400 nm
The lines on the spectrum are the wavelengths of the light produced by the discharge through a hydrogen gas.
What is this light made of?

26. The Photon: a massless particle
We’ve always thought of light as a wave, because it behaves like a wave in many cases (e.g. refraction, reflection, diffraction…). However, Einstein discovered that in some instances light behaves like a particle. He called these “particles” PHOTONS. His observations extend to all electromagnetic waves.
EM waves
Oscillations of electric and magnetic fields
Carry energy
Higher frequency = higher the energy
Photons
Packets of EM waves
Are packets of energy
Energy depends on frequency
What are they made of?
What are they made of?
Click on the questions in the boxes to reveal the answers!
What do they carry?
What do they carry?
How is the energy carried affected?
On what does their energy depend?

27. Photons emitted by filament lamp
Representing a photon
So, why does a photon behave like a particle?
It is a packet of electromagnetic energy  gives the idea of an “item” occupying a certain space, and not a continuum like a wave propagating in space
It travels in one direction only. So, a light bulb emits photons in all possible directions, with each photon travelling in one direction only.
The energy of a single photon is “quantized” and measurable. So, if a single photon hits a surface, it is a bit like a ball hitting a wall.
Photons emitted by filament lamp

28. Energy of a photon
We can measure the energy of a photon using Einstein’s equation:
h = 6.63 x Js  Planck constant
f = frequency of photon/electromagnetic radiation
c = 3 x 108 m/s  speed of light in a vacuum
l = wavelength of photon/electromagnetic radiation