P7 Radioactivity Flashcards
Becquerel
Studied the fluorescent glow of uranium
Looked to see if it reacted with photographic properties in light and dark
Discovered radiation - the powerful ray
Marie Curie
Found that salts emitted radiation all the time
Sampled dust
Discovered new radioactive elements called polonium
Ernest Rutherford
Carried out tests to see what stops radiation
Puts different materials between substance and a detector
Discovered alpha was stopped by paper
Beta goes through paper and is stopped by metal
Plum Pudding model
• circle with positive and negative charges
• JJ Thompson
• discovered in 1904
Nuclear model
Atom shape with shells
Protons and neutrons
Discovered in 1911
Ernest Rutherford
Solid Sphere model
John Dalton
1803
Planetary model
Bohr
Founded in 1913, electrons are in shells and there is a nucleus
• use today
Rutherford’s Experiment
Fired some alpha particles at a very thin sheet of gold foil (only a few atoms thick)
If the Plum Pudding model was correct, the particles should have travelled straight through and only be slightly deflected - did not happen
• some of the alpha particles went straight through
• some particles were deflected through large angles
• a very few alpha particles were reflected straight back
Alpha radiation
Image = two protons and two neutrons
Charge = +2
Absorbed through paper
Penetrating range = up to 5 cm
Ionising value is the highest
Beta radiation
Image = unstable electron
Charge = -1
Absorbed by thin metal aluminium
A few meters penetrating range
Medium high penetration
Gamma radiation
Wave
No charge
Absorbed by lead and thick concrete
Penetrating range = km s if not obstructed
Low ionising value
Alpha decay
a 4
2
Beta decay
B 0
-1
Gamma decay
Stays the same
What makes an atom radioactive?
Unstable elements/ unstable nucleus
