Radioactivity Mod:6 Flashcards
Explain Rutherford scattering experiment
A stream of alpha particles from a radioactive source is fired at a very thin gold foil when alpha particles from the source strike a fluorescent screen a tiny visible flash of light is produced
Most of the first charged alpha particles went straight through the foil therefore the atom must mainly be empty. Space
Some alpha particles were deflected through large angles so the centre of the atom must have a large positive charge to repel positive gold ions
Particles were deflected by angles greater than 90° therefore the nucleus must be tiny
Most of the mass must be in the nucleus since the alpha particles with high momentum are deflected by the nucleus
What is the atomic number and what is its symbol?
The atomic number is the number of protons in the nucleus and the the symbol is Z
What is the atomic number and what is its symbol?
The atomic number is the number of protons in the nucleus and the the symbol is Z
What is the nucleon number and what is it symbol?
The nuclear number also called the mass number has the symbol A and it tells you how many protons and neutrons are in the nucleus?
What is an isotope?
Atoms with the same number of protons but different number of neutrons are called isotopes however changing the neutrons does not affect the atoms chemical properties. It only affects the stability of the nucleus.
Explain radioactivity
This is when an isotope is not stable therefore they admit atomic particles and or energy decay will leave behind a more stable nucleus for an individual nucleus. The decay process is spontaneous and random.
Explain how a geiger Muller tube is used to detect radioactive sources 
This is a metal tube filled with argon gas. The tube has a thin wire down the middle and a voltage between the wire and the casing. The tube is good at detecting alpha and beta particles however not so good at detecting gamma particles.
When the radioactivity enters the tube ionises the gas in the tube this produces a pulse of current which is then amplified and passed to the counter
Define count rate
The number of ionisation detected per unit time
What is a radionuclide
An unstable nucleus which emits radioactivity
Define random in terms of radioactivity
Cannot predict when a particular nucleus will decay
Define spontaneous in the terms of radioactivity
It cannot be influenced by external factors such as temperature pressure, chemical reaction, et cetera
Explain the properties of alpha particles
Alpha particles are helium nuclei so have a charge of +2e
They have a relatively high mass and low speed and they interact easily with atoms in a substance
When they collide with atoms, it prevents them from passing through materials therefore alpha particles have a very short range and low penetration
They only travel around 2 to 3 cm in air
They are stopped by skin or a piece of paper
 explain properties of beta particles
Beta particles are electrons so they have charge -e
They have a very low mass and a high speed therefore they interact less easily than other particles with atoms in a substance
They can travel up to 1 m through air and threes some obstacles such as
However, they are stopped by a 3 mm thick layer of aluminium
Explain the properties of gamma radiation
Gamma radiation has no mass and travels at the speed of light therefore gamma rays collide in infrequently with atoms in a substance
Have a greater range and a considerably more penetrating than alpha or beta particle
They can travel long distances through air through pieces of paper and aluminium foil
Several centimetres of lead or several metres of concrete are needed to stop the passage of gamma
Define activity
The rate at which nuclei decay
