P4-Atomic structure Flashcards
What did Henri Becquerel discover?
That radiation from uranium had passed through the paper but not the metal key discovering radiation
How can you detect radioactivity?
By using a Geiger counter connected to a Geiger-Müller tube every time a particle of radiation enters the tube a click is heard
What types of radiation did Ernest Rutherford discover?
alpha (α) and beta (β) radiation-gamma (γ) rays were discovered later
What is a radioactive source?
A substance containing unstable nuclei that become stable by emitting radiation
What is the radius of an atom?
1 x 10⁻¹⁰m
What is the radius of a nucleus?
1 x 10⁻¹⁴
Describe the ‘plum pudding’ model and who came up with it
J.J. Thomson theorised that an atom was a ball of positive charge with negative electrons embedded within-Rutherford disproved this
Describe the gold leaf experiment and who it was conducted by
Positively charged alpha particles were fired my Rutherford into a gold leaf and he deducted the size of an atom, that atoms are mostly empty space and that the nucleus of an atom is positively charged
What did Niels Bohr theorise?
Electrons in an atoms orbit the nucleus at specific distances and specific energy levels
What are isotopes?
Atoms of the same element with different numbers of neutrons
What is the mass number (relative atomic mass)
The number of protons + neutrons
What is the atomic number (proton number)
The number of protons-defines what element something is
What is radioactive decay?
When an unstable nucleus becomes stable by emitting alpha (α), beta (β) or gamma (γ) radiation
What is ionising power?
How easily radiation can knock particles out of an atom
List the —- of an alpha (α) particle
A) What it is made up of
B) Speed
C) Relative atomic mass
D) Charge
E) Ionising power
F) Penetrating power
G) Range in air
H) Affect on nucleus
A) 2 protons, 2 neutrons
B) Slow: 5-7% speed of light
C) 4
D) +2
E) High
F) Low: cannot penetrate paper
G) Not far: 5-10cm
H) -2 atomic number - 4 mass number
List the —- of a beta (β) particle
A) What it is made up of
B) Speed
C) Relative atomic mass
D) Charge
E) Ionising power
F) Penetrating power
G) Range in air
H) Affect on nucleus
A) Electron + a neutron changes into a proton
B) High: 90% speed of light
C) 1/2000
D) -1
E) Medium
F) Medium: cannot penetrate aluminium
G) Medium:1-2m
H) +1 atomic number
List the —- of a gamma (γ) particle
A) What it is made up of
B) Speed
C) Relative atomic mass
D) Charge
E) Ionising power
F) Penetrating power
G) Range in air
H) Affect on nucleus
A) Weightless packets of energy called photons
B) Highest - 100% speed of light
C) 0
D) 0
E) Low
F) High: cannot penetrate lead
G) Infinite
H) Lower energy
Why are neutrons emitted by some radioactive substances?
As alpha particles may collide with an unstable atom causing a neutron to escape and making the unstable nuclei even more unstable.
List the —- of a neutron
A) What it is made up of
B) Speed
C) Relative atomic mass
D) Charge
E) Ionising power
F) Penetrating power
G) Range in air
H) Affect on nucleus
A) 1 up quark, 1 down quark
B) Very slow: 2000m/s
C) 1
D) 0
E) nothing
F) Extremely high: anything
G) A few metres
H) Makes a radioactive isotope
How do you calculate alpha (α) radiation’s effect on an atom?
You minus 4 from the mass number and 2 from the atomic number
How do you calculate beta (β) radiation’s effect on an atom?
You add 1 on to the atomic number
What is radioactive contamination?
Picking up radioactive material-you’ll still be exposed to it even after you’ve left the area
What is irradiation
Being exposed to radiation without coming into contact with it
List ways radiation can be used (7)
- Thickness monitoring
- Radioactive tracers
- Carbon dating
- Smoke alarms
- Radio-therapy (to destroy cancerous tumours)
- Sterilisation
- Gamma cameras
What is the half life of a radioactive isotope?
The average amount of time it takes for the number of nuclei of the isotope to half
What word would you use to describe the process of radioactive decay?
Random
Why is energy released in a nuclear reactor?
Nuclear fission
What starts nuclear fission
A neutron fired into a uranium-235 atom
What other element is fissionable aside from uranium?
Plutonium-239
When nuclear fission is undergone what does it release?
2 or 3 neutrons (called fission neutrons) at high speeds
energy, in the form of gamma radiation + the kinetic energy stored in the fission neutrons and the fragment nuclei
What is it called when there is a chain reaction of fission events meaning that neutrons released by previous fission events start new ones?
spontaneous fission
Describe the inside of a nuclear reactor
Uranium fuel rods spaced out evenly in the fuel core as well as control rods-to absorb surplus neutrons , a pressuriser, and it is all filled with water to harness the thermal; energy that drives turbines to produce energy
What are fusion reactions?
The process of forcing the nuclei of two atoms together so they form a single, larger nucleus
How can nuclear fusion be brought about?
By making 2 light nuclei collide at very high speed
What object in our solar system is made via nuclear fusion?
The sun
Describe a complete fusion reaction
1) 2 protons fuse together forming a heavy hydrogen-2 nucleus thus creating other particles
2) Two more protons collide separately with two hydrogen-2 nuclei turning them into heavier hydrogen-3 nuclei
3) The two heavier nuclei collide to form the helium-4 nucleus releasing 2 protons.
4) The energy released at each stage is carried away of the product nucleus and other particles emitted
How does a Fusion reactor work?
The plasma of light nuclei need to be heated to very high temperatures by an electric current before the nuclei will fuse-this is because they need to overcome their repelling charges. It is contained by a magnetic field as if it touched the reactor walls it would go cold and fusion would stop
Why are fusion reactors promising for our future?
- Fuel for fusion reactors is easily available-heavy hydrogen is naturally present in sea water
- The reaction product is a non-radioactive gas-harmless compared to fission reactors
- The energy released could be used to generate electricity
List nuclear issues
- Background radiation
- Nuclear waste
- Chernobyl and Fukushima
- New nuclear reactors
- Half-lives and instability
- Radioactive risks
What is the problem with background radiation and what causes it?
There is always radiation in the atmosphere but most background radiation is caused by Radon gas that seeps into homes and underground pipes that aren’t managed correctly-it can cause cell mutation and cancer
What is the problem with nuclear waste?
Used fuel rods have to be stored in water for up to a year to cool them down. Also, radioactive isotopes have to be stored in secure conditions for years to prevent radioactive contamination
What are the problems with Chernobyl and Fukushima?
When the nuclear reactor in Chernobyl, Ukraine exploded a cloud of radioactive material spread all over Europe-30 people died 100k evacuated. In Fukushima 20km was shut down and around Chernobyl and Fukushima still is
What are the issues with new nuclear reactors?
Most of the world’s current nuclear reactors will need to be replaced with 3rd gen nuclear reactors due to longevity, environmental and safety reasons leading to a massive cost.
What are the problems with half lives and instability?
Radioactive isotopes have a large range of half-lives and those with shorter ones emit a lot of radiation in a short amount of time.
What are the issues surrounding radioactive risks?
If someone has a high dose of radiation there is a high chance they develop cancerous cells or even that living cells are destroyed. There is still a small chance with smaller radiation dosages
What units of measurement are used to express radiation dosage?
sieverts (Sv)
millisieverts (mSv)
