Radioactivity Flashcards
What is the SI unit for radioactivity?
Becquerel (Bq)
Why is the mass found in the centre of the atom?
Because protons and neutrons are found inside the nucleus, the nucleus holds most of the atoms mass
What is the use of symbols such as 12 C 6 to describe particular nuclei?
6 protons, +6 neutrons = atomic number
12 = total mass number
Atomic (proton) number
is the number of protons in the nucleus of an atom
Mass (nucleon) number
is the total number of protons and neutrons in the nucleus of an atom
Isotopes
is an atom of the same element, i.e. it has the same number of protons/same atomic number, but has a different number of neutrons/different mass number.
Alpha (α) particles
are high-energy particles made up of 2 protons and neutrons. And is usually emitted from nuclei that are too large. Their ionising power is very strong
Beta (β−) particles
are high energy electrons emitted from the nucleus. And emitted by nuclei that have too many neutrons. Their ionising power is medium
Gamma (γ) rays
are high energy electromagnetic waves
And are emitted by nuclei that need to lose some energy. Their ionising power is weak
Investigation of penetrating powers
- Connect the Geiger-Muller tube to the Geiger counter and measure the background radiation for over a minute
- Repeat to get an average
- Place the radioactive source 3cm away from the tube and take a reading over a minute
- Take a set of absorbers: some paper, several different thicknesses of aluminium (increasing in 0.5mm intervals) and different thickness of lead
- Place these absorbers between the source and the tube and take another reading over a one minute interval
- Repeat with another radioactive source
Alpha decay
· 2 protons and 2 neutrons are lost
· Mass number decreases by 4
· Atomic number decreases by 2
Beta decay
· 1 neutron is converted to an electron (lost from the atom) and proton
· Mass number is unchanged
· Atomic number increases by 1
Gamma decay
· Energy is lost from an atom in the form of an electromagnetic wave
· Mass number is unchanged
· Atomic number is unchanged
How Geiger Müller detector detects radiation?
when connected to a counter, the detector will be able to measure radioactivity
How a Photographic film detects radiation?
radiation will cause photographic film to darken
Ionisation
is the process by which ions are formed by the gain or loss of electrons from an atom or molecule
Background radiation on Earth
there are alot or rocks on Earth that contain radioactive substances, therefore we are constantly exposed to ionising particles
Background radiation in Outer Space
we are exposed to cosmic rays which are isonising radiations in which our atmosphere protects us from. The two sources that make up the background radiation are: man made and natural
Half-life
is the time taken for half the nuclei of that isotope in any sample of decay
Radioactivity in Medicine
radioactive tracers help doctors to examine the insides of our bodies
Radioactivty in Industry
radioactive tracers are used to detect leaks in underground pipes
Contamination
the unwanted presence of materials containing radioactive atoms on other materials
Irradiation
The process of exposing a material to alpha, beta or gamma radiation
Dangers of Radiation
· Ionising radiation can damage human cells and tissues
· If the atoms that make up a DNA strand are ionised then the DNA strand can be damaged
· If the DNA is damaged then the cell may die, or the DNA may be mutated when it reforms
· If a mutated cell is able to replicate itself then a tumour may form
How can uranium-235 atom be split?
during fission, U-235 atoms absorb loose neutrons. This causes U-235 to become unstable and split into two light atoms called fission products
Nuclear fission as a source of energy
the process where heavy atoms are split into smaller, lighter atoms. This releases energy
Radioactive decay as a source of energy
within the core of the Earth, radioactive isotopes of elements such as uranium, thorium and potassium provide a large proportion of the heat within the Earth through radioactive decay
Isotopes
are atoms of the same element (or the same atomic number) and different mass numbers (different number of neutrons)
