2.5 Atomic Physics Flashcards
(24 cards)
What are isotopes
Atoms with the same number of protons but different numbers of neutrons (same atomic number but different mass number)
How to find proton, neutron, and electron of an element
Atomic number = protons or electrons
Mass number = protons + neutrons
ᴬᴢE (z is subscript)
What is A and what is Z
A is mass number
Z is atomic number
What are Rutherfords 3 findings
- Most of the alpha particles passed straight through the gold foil, meaning the atom mostly consists of empty space.
- Large angle deflection (bouncing back) indicates that the alpha particles were being repelled by a particle with the same positive charge. There must be a concentration of positive charge in the atom
- Very few alpha particles bounced straight back, meaning they encountered a very dense, positively Most of the atom’s mass must be concentrated in a very small and positively charged nucleus.
What is an alpha particle
A helium nucleus. Mass of 4 and charge of +2. (positively charged)
What is a beta particle
High energy/ speed electron (negatively charged)
What is a gamma ray
Electromagnetic wave (photon)
What the penetration strength of an alpha particle
Alpha particles have the lowest penetrating power and travel only a few cm in air and can be stopped by a sheet of paper because of their large size which makes them more likely to bump into the molecules of whatever they are penetrating/ interacts strongly with matter and lose energy rapidly, stopping them quickly.
What the penetration strength of an beta particle
Beta particles have a moderate penetrating ability, can travel up to a few metres in air but stopped by a 5 mm thick sheet of aluminium. Due to its small size it can travel further.
What the penetration strength of an gamma ray
Gamma rays are most penetrating and can pass through human tissue. Most gamma rays will be stopped by a few cm of lead but some may still pass through. It has no mass so it’s very penetrating.
What is JJ Thompson’s atomic model
“Plum pudding” model, proposed that an atom is a positively charged mass/sphere with negatively charged electrons embedded and spread out evenly within. Overall, the atom is neutral.
What is nuclear fusion
Two light atomic nuclei combine to form a single heavier one
What is nuclear fission
A large unstable nuclei split into smaller nuclei
Mostly requires neutrons and makes a few neutrons to start a chain reaction
What is radioactive decay
Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation.
What is radioactive half-life
The average amount of time taken for the activity to halve, or the time taken for half of the atoms in a sample to decay into something else.
Why do smoke detectors use alpha particles
Alpha particles have strong ionising ability, therefore they are able to strip electrons from the air molecules inside the smoke detector. The ionised air molecules flow between the charged plates, which is detected as a flowing current. Without the alpha particles there will be no ionised particles and no current will flow.
What is are the parts of a radiation badge (dosimeter)
Three seperate windows: an open window, aluminium window, and lead window. There is a photographic film at the behind the windows that darkens when exposed to radiation.
Which window bocks what type of radiation and why
Open window doesn’t block anything, aluminium blocks beta radiation, and lead blocks gamma radiatoin
Formulas
E=mc^2
E=Pxt
What is ionisation
Ionisation is the removal or addition of an electron, to or from an atom, leaving the atom in a charged state.
Why
Beta symbol
0 (superscript) -1 (subscript) B or e
Alpha symbol
4 (superscript) 2 (subscript) He or a
Gamma symbol
0 (for both superscript and subscript) Y
