P6.1 - Radioactive Emissions Flashcards
What are subatomic particles
Particles from which an atom is made
What is the relative mass of a proton
1
What is the relative mass of a neutron
1
What is the relative mass of an electron
0.0005
What does the charge on the nucleus depend on?
The number of protons in it
Why do the nuclei of different elements have different masses
Atoms of an element can have different numbers of neutrons.
Neutrons don’t have a charge (they are neutral) so they change the mass of the nucleus without changing the charge
What are isotopes
Atoms of an element with different numbers of neutrons but the same number of protons and electrons
What is the mass number
The number of protons and neutrons in the nucleus of an atom
What is the atomic number
The number of protons in the nucleus
How do you calculate the number of neutrons in the nucleus
Mass number - atomic number
What does the 12 in carbon-12 represent
The total number of subatomic particles in the nucleus
What is a stable isotope?
An isotope that is not radioactive
What do unstable nuclei emit?
Radiation
What is an alpha particle (include symbol and equation)
It is the nucleus of a helium atom
Symbol: a
Equation : 4
He
2
What is a beta particle (include symbol and equation)
It is a fast moving electron
Symbol: ß
Equation 0
e
-1
What is gamma radiation (include symbol and equation)
It is an electromagnet wave
Symbol : Y
Equation : none
What is a neutron (include symbol and equation)
It is a particle in the nucleus
Symbol : n
Equation 1
n
0
A nucleus does not contain electrons so where does the beta particle come from
Neutrons can decay to make a proton and an electron
What can you use to detect radiation
A Geiger counter
How does a Geiger counter work
It clicks when radiation enters it
Each click is a tiny current that is produced when the radiation ionises atoms of the gas inside the tube
What is penetrating power?
It is the ability of radiation to travel through a material
Which is the most penetrating alpha beta or gamma?
Gamma
What material stops alpha radiation
Paper
Skin
What material stops beta radiation
Aluminium
What stops gamma radiation?
A few cm of lead
A few m of concrete
However some gamma radiation still can get through
What is ionising radiation
It is Radiation emitted by radioactive material
It can remove electrons from its atoms to produce positively charged ions
Which has the most ionising power alpha beta or gamma radiation
Alpha
Which has the least ionising power alpha beta or gamma radiation?
Gamma
Write the equation for the alpha decay of the nucleus for Pu-240
240 236 4
Pu —> U + He
94. 92 2
What happens in alpha decay?
Two protons and two neutrons join to form an alpha particle
This is then emitted from the nucleus
What happens in beta decay?
A neutron decays for a proton and an electron
The electron is emitted as a beta particle
The number of neutrons goes down by one
The number of protons goes up by 1
Write the equation for the beta decay of the nucleus of C-14
14 14 0
C —> N + e
6 7 -1
What happens in gamma decay
Gamma rays are electromagnet waves so they don’t have mass or charge
They are usually emitted alongside alpha and beta decay
What happens in neutron emission ?
When some nuclei decay they produce nuclei with large numbers of neutrons.
These nuclei can emit neutrons to make the nucleus more stable
Write the equation for the neutron emission of He-5
5 4 1
He —> He + n
2 2 0
What is activity
It is the number of decays per second
What unit is activity measured in
Becquerels (Bq)
What is half life
The time it takes for the activity to half
The time for the nuclei of half the atoms ri decay
Decay is random, half life if constant
True
What happens to the atoms that decay
If they emit alpha or beta particles they change to the atom of a different element and eventually they become stable
