Flashcards in P4:Atomic structure Deck (59):
The further an energy level is from the nucleus, the more...
Energy an election in that energy level has.
How can electrons move between energy levels? (2)
1) Absorbing electromagnetic radiation.2) Releasing electromagnetic radiation.
What happens if an electron in an outer energy level absorbs electromagnetic radiation?
It can leave the atom.
What happens if an atom loses one or more electrons?
It turns into a positively charged ion.
What is the number of protons in an atom called?
It's atomic number.
What gives the nucleus a positive charge?
The protons in the nucleus.
The mass number of an atom is the sum of...
The number of protons and the number of neutrons.
What is an element?
A substance only containing atoms with the same number of protons.
What are isotopes?
Atoms of an element with the same number of protons but different number of neutrons.
Isotopes of an element have the same…But a different...
Same = atomic number.Different = mass number.
What do isotopes do if they are unstable?What is this process called?
They emit (give out) radiation from their nuclei to try and become more stable.This process is called Radioactive Decay.
What is the radiation emitted from unstable isotopes called?
Name the four different types of nuclear radiation call
1) Alpha2) Beta3) Gamma4) Neutrons
An alpha particle is…
Two neutrons and two protons like a helium nucleus.
A Beta particle is...
A fast moving electron.
Gamma rays are...
Waves of electromagnetic radiation.
What is Ionising radiation?
A radiation that can knock electrons off atoms and turn them into ions.
What is the ionising power?
How easily a radiation can knock electrons off atoms and turn them into ions.
Alpha, beta and gamma rays are all types of....
ALPHA PARTICLES.What is their ionising power?
BETA PARTICLES.What is their ionising power?
GAMMA RAYS.What is their ionising power?
ALPHA PARTICLES.What is their range in air?
A few centimetres.
BETA PARTICLES.What is their range in air?
A few meters.
GAMMA RAYS.What is their range in air?
A long distance.
ALPHA PARTICLES.Stopped by...
A sheet of paper.
BETA PARTICLESStopped by...
A sheet of aluminium.
GAMMA RAYS.Stopped by...
Thick sheets of lead or metres or concrete.
Nuclear equations are a way of showing radioactive decay. How are they normally written?
Nucleus before decay ---> nucleus after decay + radiation emitted. The total mass and atomic numbers must be equal on both sides.
What is alpha decay?
When an alpha particle is emitted from a radioactive nucleus.
Does alpha decay increase or decrease the charge and mass of the nucleus?
What is Beta Decay?
When a beta particle is emitted from a radioactive nucleus.
During a beta decay, what is a neutron in the nucleus turned into?
Does Beta Decay increase or decrease the charge of the nucleus?
Do Gamma rays change the charge or mass of the nucleus?
No because they are a way of getting rid of extra energy from the nucleus.
The radiation given out by a radioactive decay can be measured with: (2)
1) A Geiger Muller tube.2) Counter Detector.
The number of decays the counter measures every second is called the...
What is the activity of a radioactive source?
The rate at which it decays - this means how many unstable nuclei decay every second.
What is activity measured in?
Becquerels. BQ. 1 BQ is 1 Decay per second.
Radioactive decay is entirely random. What does this mean you can't do?
You can't predict exactly which nucleus in a sample will decay next or when any of them will decay.
Since you can't predict exactly when radioactivity happens, what can you do instead?
You can predict how long it will take for half of the nuclei to decay. This is known as half life.
What is half life?
The time taken for the number of nuclei of a radioactive isotope in a sample to halve.
Half life is also...
The time taken for the count rate or activity of a sample to fall to half of its initial value.
The half life of a radioactive sample will always be the...
Same. This meant it doesn't matter what activity you start with when doing half life calculations.
How do you calculate half lives?
You just need to know how long it takes for the activity or count rate of the source to halve.
How can Ionising Radiation be bad?
They can enter living cells and ionise atoms in them which causes damage to the cell. This may cause cancer or kill cells of completely.
Exposure to radiation is called...
Objects near a radioactive source can be irradiated by it. What does this mean?
Radiation from the radioactive source will reach the object.
The further you are from a particular source, the less...
Radiation will reach you.
To help stop irradiation happening, you should: (3)
1) Store radioactive sources in lead lined boxes when they're not being used.2) Stand behind barriers that will absorb radiation when using sources.3) Keep the source as far away from you as possible e.g. Hold it at arm's length.
What is contamination?
When unwanted radioactive atoms get into or onto an object.
What do contaminating atoms do?
They might then decay and release radiation which could harm you.
Being contaminated by a source may cause more damage than if you are irradiated by the same source. Why?
Because you may carry it for a long time.
To help stop contamination, you should...
Wear gloves and use tongs when handling radioactive sources.
What are the most dangerous sources to be irradiated by?
Beta and Gamma.
Why are Beta and Gamma the most dangerous sources to be irradiated by? (2)
1) they have long ranges which means more radiation will reach you from a beta or gamma source than from an alpha source at the same distance.2) they can penetrate through your body and may damage your organs. Alpha isn't as dangerous as it can't get through skin and is easily blocked.
What is the most dangerous source to be contaminated by INSIDE the body?
Alpha because they are the most ionising type of radiation. Beta and Gamma are less damaging because they are less ionising.
What source is the least dangerous inside the body and why?
Gamma sources because gamma rays are the least ionising type of radiation and they mostly pass straight out without any damage.