Radioactive Decay Flashcards
What did Marie Curie discover?
All uranium compounds are radioactive and contain two other elements; polonium and radium.
What is natural radioactivity
The process where substances emit radiation freely in nature
Why could the nuclei of some atoms be unstable?
They may have too much energy or the wrong number of particles in the nucleus
How do atoms make themselves more stable?
They emit particles and/or energy from the nucleus
What happens if a nucleus emits a particle
It becomes the nucleus of a different element. This is radioactive decay
What are the particles given out during radioactive decay called?
Radiation or radioactive emissions
What is radioactivity
The spontaneous (random) decay of the nuclei of atoms by emission of particles and/or energy
How did Henri Becquerel discover that uranium compounds emit radiation spontaneously?
He left a piece of uranium in his drawer next to a photographic plate wrapped in black paper. This plate showed a darker section when it was developed; a shadow had formed, indicating something was been emitted (radiated) from the uranium that would effect photographic film.
What is ionisation?
When radiations hits a neutral atom, some of the energy from the radiation is passed to the atom. This energy can cause an electron from the atom to escape, leaving the atom with a positive charge. This positively charged atom is an ion, and this process is called ionisation.
Why can ionisation be dangerous?
It is ionisation that makes radioactive substances so dangerous. Living cells can be damaged if molecules in the cell are ionised, and this can kill cells or cause radiation burns and cancers. (It damages DNA.) the more radiation, the more likely it is that cancer will occur
All atoms are made up of..
Protons, neutrons and electrons
What is the only difference between one atom and the next?
The number of protons, electrons and neutrons in the atom.
How much do neutrons and protons way in comparison to electrons
2000 times as much as an electron
What charge to protons have
Positive
What charge to electrons have
Negative
What charge to neutrons have
No charge
How would you describe an atom?
It is not a solid thing. Protons and neutrons are tightly held together by a strung nuclear force in the nucleus and electrons spin around them.
Are atoms almost full, or almost empty?
Almost empty
How would you describe an atomic structure
There is a specific notation used to describe the number and type of particles associated wit jam atom. Eh, 4 = mass number He 2 = number of protons
What is the mass number?
How many particles are in the nucleus (how many protons and neutrons)
What is the atomic number
How many protons there are in the nucleus
What does it mean if an atom is neutral
The number of electrons in an atom is the same as the number of protons
What happens if the numbers of protons and electrons am atom are not equal
It becomes a charged particle ion
All atoms of a certain element will have…
The same number of protons in the nucleus
What do the number of protons on an element decide?
How the elements is going to behave chemically and therefore what element the atom belongs to. If the number of protons in an atom changes, the type of atom is changed. (It becomes an atom of another element)
What is an isotope?
Isotopes have the same number of protons but a different number of neutrons
What is the symbol for alpha particles?
4
α
2
Or
4
He
2
What is the symbol for beta particles?
In beta radiation, a neutron in the nucleus split up into a proton plus an electron. The proton stays in the nucleus and the electron is ejected at high speed, so
0
β
-1
Or
0
e
-1
What is the symbol for gamma rays?
Also known as electro-magnetic radiation
γ (no charge, no mass, no nothing)
Why do particles that ionise strongly have a low penetrating power?
They lose energy each time they ionise an atom
Is radioactive decay affected by external conditions?
No
Charge of an alpha particle
+ 2
Charge of a beta particle
- 1
Charge of a gamma ray
0
Speed of an alpha particle
Slow
Speed of a beta particle
Fast
Speed of a gamma ray
Very fast
Ionising ability of an alpha particle
High
Ionising ability of a beta particle
Medium
Ionising ability of a gamma ray
Low
Penetrating power of an alpha particle
Low
Penetrating power of a beta particle
Medium
Penetrating power of a gamma ray
High
What is an alpha particle stopped by
Paper
What is a beta particle stopped by
Aluminium
What is a gamma particle stopped by
Lead
What are nuclear decay equations used to describe
The decay of nuclei by emission of radioactive particles and the product nuclei
What do nuclear decay equations have to balance
- the total number of protons must be the same before and after the reaction
- the total number of nucleons must be the same before and after the reaction
In alpha decay, the product nuclei has…
Two less protons and two less neutrons
In beta decay, the product nuclei has…
One more proton and one less neutron
are gamma rays emitted with change of nuclei
No
Why does the nucleus emit an electron when it emits a beta-particle?
The neutron has changed into a proton and an (emitted) electron
Where is background radioactivity
All around us in the atmosphere.
Where does background radioactivity come from?
Radioactive rocks in the ground, radon gas in the air and cosmic rays from outer space
What do you use to detect radioactivity
A Geiger counter. It clicks each time a particle of radiation from a radioactive substance enters the Geiger tube.
What does the number of clicks per second represent I’m a Geiger counter
The activity of the sample. The higher the activity the more radioactive the sample
How would you accurately measure the activity of a sample of a radioactive substance
First measure the background radioactivity. This can then be subtracted from the measured sample activity to obtain a true reading
What is the half life of a substance?
The amount of time it takes for half of the atoms in a sample to decay. This can vary from being less than a second to taking millions of years
What is the half life for a given isotope
Always the same
What does a half-life not depend on
How many atoms you being with
What does the half life of an elect indicate
How stable an isotope is. The longer it takes to decay, the more stable it is
What is decays per second measured in
Becquerel’s (Bq)
