Radioactivity Flashcards
Which particles are found in the nucleus of the Atom?
Protons & Neutrons
Which particle did Rutherford fire at gold leaf in his famous experiment?
Alpha particles
What were the main observations and conclusions from Rutherford’s famous gold leaf experiment?
1) Most α go through = mostly empty space
2) Very few α deflected by large angles = dense central nucleus (very massive, very small)
3) Some α deflected by small amounts = nucleus has charge
How big is an atom?
1 × 10 -10 m
(0.0000000001 metres)
An isotope has the same number of ________ but a different number of ________.
An isotope has the same number of PROTONS but a different number of NEUTRONS.
The mass number is:
Protons + neutrons
Electrons exist in shells around the nucleus. Sometimes they jump up a level - how?
By absorbing just the right amount of energy to make the jump.
Sometimes the electrons orbiting a nucleus absorb energy and jump up a level. When they drop back down what happens?
The emit electromagnetic radiation.
What is ionisation?
When an electron gains enough energy to free itself from the nucleus, leaving an ion behind.
What causes the majority of background radiation?
Radon gas
Name the three main types of ionising radiation
Alpha
Beta (+/-)
Gamma
What are the main properties of alpha radiation?
α
2 protons, 2 neutrons (He nucleus)
Charge: +2
Highly ionising
Range in air: few cm
Stopped by paper/skin
What are the main properties of beta radiation?
β
High speed electron (-) or positron(+)
Charge: -1 (beta minus) +1 (beta plus)
Moderately ionising
Range in air: few metres
Stopped by aluminium
What are the main properties of gamma radiation?
γ
Electromagnetic wave
No Charge, No mass
Weakly ionising
Range in air: few km - infinite
Stopped by lead or metres of concrete
What happens to the mass and atomic number of a nucleus when it undergoes alpha decay?
Mass number goes down by 4
Atomic number goes down by 2
What happens to the mass and atomic number of a nucleus when it undergoes beta minus decay?
Mass number remains the same
Atomic number increases by 1
What happens to the mass and atomic number of a nucleus when it undergoes beta plus decay?
Mass number remains the same
Atomic number decreases by 1
What happens to the mass and atomic number of a nucleus when it undergoes gamma decay?
No change to either Mass or Atomic number
What happens to the mass and atomic number of a nucleus when it undergoes Neutron decay?
Mass number goes down by one
Atomic number remains the same
Which type of radioactive decay involves a proton becoming a neutron?
A Proton becomes a neutron Plus a Positron in beta Plus decay
(Remember all the Ps!)
Define half life
The average time taken for half of the radioactive nuclei in a sample of radioactive material to have decayed.
What unit is activity measured in?
Becquerels (Bq)
Describe two effects of ionising radiation on the human body.
1) Radiation burns/radiation sickness
2) Mutation of DNA within cells leading to cancer
What is the difference between contamination and irradiation?
Irradiation: Only while you are in range of the source. Stops when you move away.
Contamination: You carry the source with you - (on clothes or ingested/inhaled) you continue to be irradiated.
