Radioactivity Flashcards
Solid sphere atomic model
John dalton
1803
Different atoms for each element
Plum pudding model
J.J. Thompson
1904
Discovered electrons
Nuclear model
Ernest Rutherford
1911
Gold leaf experiment
Discovered nucleus
Discovered empty space in atoms
Planetary model
Niels Bohr
1913
Orbiting electrons
Quantum Model
Erwin Schrodinger
1926
Electrons move in waves
Best model of the atom
Radioactive decay is…
…a random unpredictable process, when an unstable atom decays. Atoms with the wrong number of neutrons can fall apart,they regain stability by emitting alpha or beta particles.
Alpha particles
4 a
2
Helium nucleus
2+ charge
Beta particles
0 b
-1
High velocity/energy electron
-1 charge
Gamma rays
0 y
0
High frequency em wave
No charge or mass
When a neutron decays it becomes a…
…proton and electron (beta)
Alpha particles can penetrate…
… nothing, stops at paper
Beta particles can penetrate…
…paper, stopped at aluminium
Gamma rays can penetrate…
…paper and aluminium, stopped at lead
Neutrons can penetrate…
…paper and aluminium and lead, stopped at concrete
What is the largest source of background radiation?
Radon gas (50%)
What is the second largest source of background radiation?
Rocks and building materials (15%)
What is the third largest source of background radiation?
Medical - ex-rays (13%)
What is the fourth largest source of background radiation?
Food (11%)
What is the fifth largest source of background radiation?
Cosmic rays (10%)
Half life
The time taken for half of the unstable nuclei in a sample to decay, or for the activity of the sample to half, or for the count rate to half
Count rate
Number of decays recorded each second by a detector, such as a Geiger-muller tube. Measured in Becquerel (Bq)
If a half life is 2 days, how many would 4 half life’s be?
8
