P4 (physics)(book & booklet) Flashcards
What does the mass number tell you?
The number of particles in the nucleus (numbers of proton and neutrons)
What does the atomic number tell you?
Number of protons
How do you find out the number of neutrons?
Mass number - atomic number
What is the number of electrons equal to ?
Number of electrons = number or protons
What is the charge of a neutron?
0
What is the charge of a proton?
+1
What is the charge of a electron?
-1
What charge is the nucleus?
Positive (2+)
What is the overall charge of an atom?
Neutral
Define isotope
Atoms of the same element but with a different number of neutrons
Describe the plum pudding model
No nucleus
Mass is spread out
Electrons embedded in a positive charge
Describe Rutherford’s nuclear model
Mass is concentrated in the centre
Electrons orbit the positive nucleus
Most of the atom is empty spaced
What is an atom ?
The smallest piece of an element that still has the properties of that element. A building-block of matter
What is the size of an average atom?
1x 10^-10 or 0.1nm
What is a sub-atomic particle?
A particle that makes up the atom
Name the 3 sub-atomic particle
Proton
Neutron
Electron
What is the atomic nucleus ?
The central part of the atom (containing protons and neutrons)
What is the mass of a proton?
1
What is the mass of a neutron?
1
What is the mass of an electron?
0
Which sub-atomic particles are in the nucleus?
Protons and neutrons
Which sub-atomic particles orbit the nucleus?
Electrons
Which sub-atomic particle defines which element the atom is?
Proton
Explain why atoms are overall neutral (3)
Protons are positive
Electrons are negative
Atoms have the same number of protons and electrons so they cancel out
What is an ion?
An atom that is charged becuase it has lost or gained electrons
What was the ‘plum pudding’ model of the atom?
Negative charges spaced in a positive dough
What is the ‘nuclear’ model of the atom?
Positive central nucleus surrounded by negative electrons- most of atoms is empty spaced
What is gamma radiation?
An electromagnetic wave from the nucleus
Describe the structure of an alpha particle
A helium nucleus - 2 protons and 2 neutrons
What is a beta particle?
A fast moving electron
What are the three types of ‘nuclear’ radiation?
Alpha , beta particle , gamma ray
What is the unit of “activity” for a radioactive isotope?
Becquerels (Bq)
What is contamination?
When radioactive material gets into an object
The object is now radioactive
What is irradiation?
When an object is exposed to radiation
The object doesnt become radioactive
Which is the most penetrating radioactive emission?
Gamma
Which is the least penetrating radioactive emission?
Alpha
Which materials are able to stop each type of radiation?
Alpha = paper
Beta = aluminium
Gamma = thick lead or thick concrete
Describe the ionising power of alpha , beta and gamma
Alpha = strongly ionising (dangerous can destroy and damage cells and tissues very quickly)
Beta = weakly ionising
Gamma = very weakly ionising
How does beta decay occur?
A neutron in the nucleus decays to make a proton and an electron. The electron exits the nucleus as a beta particle and the proton stays in the nucleus
what does the term ‘half-life’ mean?
Time taken for the number of unstable nuclei to half
Who set up an experiment, where alpha particles were fired?
Rutherford
What did Rutherford fire the alpha particles at?
An incredibly thin piece of gold
What did Rutherford fire in his golf foil experiment?
Alpha particles
What was Rutherford expecting?
All of the particles to pass through unaffected
What happened to some of the particles he fired and why was that?
Many of the particles were deflected , with some almost bouncing back to where they came from This showed that the nucleus at the centre must be positive because positives repels from each other
What is it called when electrons could only be found at specific distances from the nucleus?
Energy levels or shells
The further away from the nucleus , the higher the what?
The higher the Energy levels or shells
What can the electrons do if they are given energy (by absorbing electromagnetic radiation)?
They can move up energy levels
Can this process (excitation) be reversed?
Yes this process can happen in reverse
If an electron moving closer to the nucleus (down an energy level) what will it give out?
It will give out some electromagnetic radiation or photon
What is meant by when some atoms are ‘radioactive’?
They have an unstable nucleus, that wants to decay. It can decay to become more stable by giving out certain types of radiation
What is meant by activity?
The number of decays/particles emitted per/each second. The unit of activity is the becquerel (Bq). 1 Bq is equal to one decay per second
What kind of process is radioactive decay?
A random process
What does it mean if radioactive decay is a Radom process?
This means you cant predict which atom will decay next, or how long it will take for any individual atom to decay
When an unstable nucleus decay , which three types of radiation can it emit?
Alpha
Beta
Gamma
What is the change to the mother nucleus on an alpha particle?
Nucleus loses 2 protons and 2 neutrons
What is the change to the mother nucleus on a beta particle?
The nucleus loses a neutron and gains proton
What is the change to the mother nucleus on gamma?
The nucleus has less energy
State the decay equation for alpha?
4
α
2
How do you do the alpha decay equation?
Take 4 away from the mass number
Take 2 away from the atomic number
Write the beta decay equation
0
β
-1
How do you solve the beta decay equation?
Mass number doesn’t change
Add 1 to the atomic number
What is alpha’s range in air?
A few centimetres
What is beta’s range in air ?
Up to 1m
What is gamma’s range in air?
Many kilometres
What is ground state?
Lowest energy and closest to the nucleus
(First shell)
What is absorption stage?
Electrons absorbs energy from Em wave or a photon
What is the excitation state?
Electron goes ‘’up’ an energy shell
Define an excited atom
Electrons have too much energy
What does the electron do to go down to a lower energy shell?
Emits energy
What is ionisation?
Removal of electrons from atoms ,leaving them with an overall charge
What does ionisation create?
Ions
What is the mass and charge of an alpha particles?
Mass = 4 because it has 4 atoms
Charge = 2+
What is the mass and charge of a beta particle?
Charge = -1
Mass = 0
What does em stand for?
Electromagnetic
What will the unstable nucleus do ?
Unstable nucleus → stabler nucleus + radiation
Are alpha particles big or small?
Big
What are direct radiation damage mostly caused by?
Alpha and beta ‘hitting’ the skin and transferring energy
What are indirect radiation damage mostly caused by?
Gamma by ionising atoms in cells
What forces act on the particles in the nucleus of an atom?
Intermolecular
What is the difference between the activity and the count rate of a radioactive source?
Activity → overall
Count rate → detected
What was JJ Thompson’s discovery that lead to the plum pudding model of the atom?
Electrons
Why is alpha particles most ionising?
Biggest particle out of Gamma and Beta
Why is gamma the most penetrating?
Because it is a EM wave
Name the three uses of radiation
Sterilisation
Smoke detectors
Paper/metal sheet manufacturing
Explain which type of radiation is used for sterilisation
Gamma
Irradiation
Most penetrating so it can kill any bacteria
Least ionising
Explain which type of radiation is used for a smoke detector
Alpha particle
Ionising enough to ionise air particles, completing the circuit
Easily absorbed (smoke)
Can’t travel far (~2cm) so it is safe to use
Explain which type of radiation is used for paper/metal sheet manufacturing
Beta radiation
Weakly ionising
Fairly penetrating
Define radon gas
Radioactive gas produced by rocks because most have small amounts of Uranian
→ Made up 49% of the background radiation
What is the Equation for real activity?
Real activity = measured activity - background activity
Give examples of the damage a radiation can cause
Burns
Tumours (cancer)
Define radioactive tracer
A radioactive source combined with a drug or biochemical agent. Injected into patient to help with diagnosis of disease
→ Radioactive sources of beta or gamma
Why is alpha not used for radioactive tracer?
Too ionising and is not penetrating so it can not travel far
What are the two types of radiotherapy?
Internal radiotherapy
External radiotherapy
Define internal radiotherapy
Direct damage to tumours cells
→ Alpha or beta particles
Define external radiotherapy
Targeting tumours from outside with gamma rays
