Atomic structure Flashcards
What is the size of the radius of one atom?
1 x 10^-10 metres
What is the size of the radius of one nucleus?
1 x 10^-14 metres
What is the mass number of an atom?
No. of protons + No. of neutrons
What is the atomic number of an atom?
No. of protons
What is an isotope?
Substances of the same element with a different no. of neutrons.
Give the order + discovery of the development of the atom.
John Dalton: Matter can’t be created/destroyed.
JJ Thompson: Plum pudding model (+electrons)
Rutherford: Gold foil experiment (+protons)
Bohr: Bohr model (+shells)
Chadwick: Neutrons
Describe the plum pudding model.
Sphere of positive charge with electrons embedded.
State the order of the discovery of the sub-atomic particles.
Electrons, protons, neutrons
Describe the gold foil experiment.
Alpha particles were shot at a layer of thin gold foil, they were much denser and should’ve been able to completely pass through. But, only some passed through, some deflected, and some rebounded. This meant there was a positive nucleus, electrons in shells and the rest was empty space.
What is meant by an unstable isotope?
Undergoes radioactive decay, so it emits something to become stable.
What is an alpha particle made up of?
2 protons + 2 neutrons (same as helium nucleus)
Describe the properties of alpha radiation.
Most ionizing
Least penetrating, blocked by paper/skin
+2 charge
Describe a beta particle.
A neutron in the nucleus decays to become a proton and an electron: the electron is the beta particle which is shot out. The proton stays in the nucleus.
Describe the properties of beta radiation.
- Moderately penetrating
- Moderately ionizing
- 1- charge
What is a gamma ray?
Electromagnetic wave of radiation.
Describe the properties of gamma radiation.
- No mass/charge
- Highly penetrating, stopped by concrete/lead
- Weakly ionising
Describe the emission of a neutron.
When there are too many neutrons in a nucleus, a neutron is released.
Define activity.
Rate at which an unstable nuclei in a sample decays (Bq)
Define count-rate.
The number of decays RECORDED each second by a detector (eg geiger muller tube)
When doing nuclear eqns, what is the symbol for Alpha particles?
(4) He
(2)
When doing nuclear eqns, what is the symbol for beta particles?
(0) e
(-1)
When doing nuclear eqns, what is the symbol for gamma?
y
What is meant by a becquerel?
no. of decays per second
What is meant by a half life?
Time taken for the no. of radioactive nuclei in a sample to halve OR Time taken for the activity/no of decays to halve.
Define irradiation.
Process by which objects are exposed to radiation.
Define contamination.
Unwanted presence of materials with radioactive atoms, which will decay and irradiate.
What 3 things determine how harmful radiation is?
Type, amount, where you’re exposed.
Generally, what makes radiation harmful?
Ionising properties
What is the exception to the rule that ionising radiation is harmful?
Alpha particles are the most ionisng, but since they’re stopped by air/skin they aren’t penetrating enough. Its most dangerous when inside the body.
Why are ionising properties dangerous?
Can enter and interact with body cells causing mutation and cancer.
What kind of precautions need to be taken when in the presence of radiation?
Gloves, lead lined box, tongs
Explain the use of alpha particles in smoke detectors.
Alpha particles are used in smoke detectors
The alpha radiation will normally ionise the air within the detector, creating a current
The alpha emitter is blocked when smoke enters the detector
The alarm is triggered by a microchip when the sensor no longer detects alpha
How is radiation used in medicine?
- Radiotherapy to kill cancer cells, can be externally (gamma) or internally (beta).
-Medical tracers to track isotopes after injecting/swallowing to see if organs work properly. - Sterilizing medical equipment.
