Radioactivity 8 Flashcards
Why are some substances radioactive?
The atom is too big as the ratio of protons:neutrons is too different, making it unstable. This causes it to lose parts of its nucleus.
Give examples of background radiation
Phones, the sun, microwaves, radio towers
What measures radiation?
Geiger Counter
Structure of an alpha particle
2 protons and 2 neutrons, equivalent to helium
Structure of a beta particle
High speed electrons
Structure of gamma radiation
high energy electromagnetic ray (photons)
What occurs in the nucleus when radiation is released?
The nucleus releases particles in the form of radiation until the new atom is stable
How do you construct decay equations for alpha particles?
Minus 2 from proton number, minus 4 from mass number
How do you construct decay equations for beta particles?
Plus 1 proton number
Charge, mass, penetrative properties and ionisation of an alpha particle
+2 charge, 4 mass, is stopped by skin or paper, highly ionising
Charge, mass, penetrative properties and ionisation of an beta particle
-1 charge, mass is 1/2000th of a proton, is stopped by aluminium, moderately ionising
Charge, mass, penetrative properties and ionisation of gamma radiation
no charge or mass, stopped by lead, low ionising
How do the properties of different types of radiation affect their deflection in electric fields?
alpha particles move towards negatively charged plates, beta move towards positively charged plates, and gamma isn’t affected
How do the properties of different types of radiation affect their deflection in magnetic fields?
alpha particles move towards south pole, beta move towards north pole, and gamma isn’t affected
Describe radioactivity in a smoke alarm
Contains alpha radiation which ionises the air causing a current to flow. This current is constant and normal. When smoke particles enter, they absorb the alpha particles and neutralise the ions therefore decreasing the current. The decrease in current causes the alarm to sound. Alpha is used as it is easily absorbed and doesn’t travel outside the alarm to harm people.
Describe radioactivity in medical tracers
Used to trace the flow of a substance through a system. Patient drinks radioactive substance and a detector is placed outside the body. They are not normally harmful as they have a short half-life and decay before too much damage. Beta or gamma are used as they pass out of the body easily.
Describe radioactivity in uranium dating of rocks
Uranium in the rocks decays into lead. The age is then calculated by how much uranium to lead is in the rock.
Atomic number meaning
The number of protons in a nucleus
Mass number meaning
The number of protons and neutrons in a nucleus
Radioactive decay meaning
The process of a nucleus breaking down and emitting radiation
Electric field meaning
A region in which a charged particle feels a force
Magnetic field meaning
A region in which a moving charged particle or permanent magnet feels a force
Geiger tube meaning
An instrument that detects the radiation released during nuclear decay. Measures the counts/second
Activity meaning
The number of decays per second
