Atoms + nuclear physics Flashcards
Where is most of the atoms mass
In the nucleus
Charge
The number of electrons is equal to the number of proton so they have no overall charge (when the number changes they become ions either anions or cations)
Rutherford’s Experiment
He fired alpha particles at gold foil and then detected the alpha particles after using a moveable detector and he found over 99% of the particles went straight through showing atoms are mostly empty space
Nuclear fission process
One neutron is fired at a nucleus of an isotope (atom with more neutrons) the isotope splits and leaves three neutrons over which are fired at another three isotopes and the process repeats- each time the isotope splits energy is released as gamma radiation which heats water into steam which spins a turbine to produce electricity
What 3 elements are used in fission
Uranium, plutonium and thorium
Control rods
Control rods limit the number of neutrons by absorbing them so the reaction still occurs but doesn’t go into meltdown
Concrete walls
Concrete walls absorb energy within the powerplant
Isotopes
Atoms of the same element can have different numbers of neutrons
Radioactive decay
Some atomic nuclei are unstable so the nucleus randomly gives out radiation as it changes to become more stable
Atomic number
The number of protons in an element is its atomic number, it is the bottom number in notation
Mass number
The total number of protons and neutrons in an atom is called the mass number, it is the top number in notation
Background radiation
Radiation is around us constantly, coming from the ground (rocks), space (cosmic) and artificial sources (weapons or nuclear disasters)
Activity
Activity is the rate a which a source of unstable nuclei decays
Activity and time
Activity (Bq) decreases over time as more unstable nuclei decay
Count rate
Count rate is the number of decays recorded each second by a detector (like a Geiger-Muller tube)
Alpha particle
An alpha particle consists of two neutrons and two protons, it is the same as a helium nucleus
Beta particle
A beta particle is a high speed electron ejected from the nucleus when a neutron turns into a proton
Gamma ray
A gamma ray is a high energy electromagnetic wave
Alpha charge, mass and symbol
Charge of +2, mass of 4, α
Beta charge, mass and symbol
Charge of -1, mass of 0, β
Gamma charge, mass and symbol
Charge of 0, mass of 0, γ
Characteristics of the 3 types of radiation
Alpha is the most ionising and the least penetrating, travels 3-5 cm in the air and is stopped by paper- Beta is in the middle, can travel 10-100cm in the air and is stopped by aluminium, Gamma is the least ionising and the most penetrating with infinite range and is stopped by thick concrete
Half- life
The time is takes for the mass, activity, count rate or number of nuclei to halve for a radioactive sample
Contamination
The unwanted presence of a radioactive substance on or in other materials
