SP6 - Radioactivity Flashcards
What are the charges on protons, neutrons and electrons?
+1
0
-1
What did the Plum pudding model say about the atomic structure of atoms?
That an atom is a mass of positively charged material with electrons scattered throughout it.
What did Rutherford’s model say about the atomic structure of an atom?
The mass is concentrated in the centre nucleus
The positive charge is in the nucleus
There are electron orbiting the nucleus
What was Rutherford experiment?
He fired alpha particles at gold foil and used detectors to see where the particles went.
How did Rutherford’s experiment disprove the plum pudding model?
Most particles went straight through the foil - shows that there is empty space between the nucleus and the electrons.
Some particles were deflected at small angles - shows that they passed closely to the nucleus
Some particles were deflected at large angles - shows that they hit the nucleus
What is the atomic number?
Number of protons (and electrons)
What does the atomic mass show?
The number of protons and neutrons.
What are isotopes?
Atoms of an element with the same number of protons and a different number of neutrons.
What happens when an electron gains energy?
It moves to a higher orbit (shell)
What happens if an electron gains too much energy?
It escapes from the atom completely - the atom becomes a positive ion
What does it mean if an electron moves to a lower orbit?
The electron is emitting electromagnetic waves. (Losing energy)
What is the name of the model we use today?
Bohr’s model
What is background radiation?
The natural low levels of ionising radiation we are constantly exposed to.
What are natural sources of background radiation?
Cosmic rays - from space
Rocks and soil - some emit radioactive radon gas
Living things - plants absorb radioactive material and pass it to food
What are artificial sources of background radiation?
Radioactive waste - from nuclear power stations
Radioactive fallout - from nuclear weapon testing
Medical - x-rays, tanning
Name the 6 main sources of background radiation.
Radon gas
Medical
Land and buildings
Food and drink
Cosmic rays
Nuclear
Which of the 6 sources does most background radiation come from?
Radon gas
Where does radon gas come from?
The radioactive decay of uranium in rocks and soil.
What do levels of radon gas depend on?
The uranium content and permeability of the rocks and soil.
What are the 3 types of radiation?
Alpha
Beta
Gamma
What is alpha radiation?
A helium nucleus
2 protons - 2 neutrons
What is the charge of an alpha particle?
2+
What is the atomic mass of an alpha particle?
4
What are beta particles?
A single electron leaving the atom.
What is the charge of a beta particle?
-1
What is the atomic mass of a beta particle?
Almost 0
What are gamma particles?
A electromagnetic wave leaving the atom.
What is the charge of a gamma particle?
No charge
What is the atomic mass of a gamma particle?
No mass
Which of the three types of radiation is the most ionising?
Alpha - most ionising
Gamma - least ionising
Which of the types of radiation has the best penetration?
Gamma - best
Alpha - worst
What stops alpha particles?
Paper
Skin
What stops beta particles?
Thin aluminium
What stops gamma particles?
Thick lead
What is a radioactive atom?
An unstable isotope.
What is half-life?
The time it takes for the activity to decrease by half
The time it takes for half the number of unstable nuclei to decay
What is activity?
The number of radioactive decays per second.
What are the units of radioactivity?
Becquerels (Bq)
Is radioactive decay random or not?
Random
Unpredictable when the atom will decay
What are the risks of excessive exposure to radiation?
Tissue damage
Cancer
Cellular damage
Skin burns
Mutations of DNA
How can we reduce exposure to radiation?
Lead lined containers - no radiation can escape
Handing sources with tongs
Film badges - keeping exposure time short
Keeping far away from sources
What is contamination?
When radiation is on or in you
What is irradiation?
When radioactive rays are hitting you.
What do you need to do if you get contaminated?
Decontaminate yourself
