19: Using the Atom Flashcards
Describe the number of protons and neutrons in isotopes of the same element
Same number of protons, different number of neutrons
Same Z, different A
What is the Z number in standard notation?
The proton number or atomic number
What is A in standard notation?
The nucleon number or mass number
What forces are balanced inside a stable nucleus?
Strong nuclear force holding it together
And the electrostatic force pushing the protons apart
What happens if the nucleus is unstable, how does it transform?
It transforms into a more stable isotope by emitting radiation
What can cause the nucleus to be unstable?
Too many neutrons
Too few neutrons
Too many nucleons in total, it’s too massive
Too much energy in the nucleus
What are the four types of nuclear radiation with symbol?
consitiuents
charge
mass
Alpha, beta–minus (beta), beta–plus, gamma

What is an atomic mass unit, u?
Roughly the mass of a proton or neutron
What is alpha radiation made of?
Two protons and two neutrons
Helium nucleus
What is the relative charge of each type of nuclear radiation?
Alpha: +2
Beta–minus: -1
Beta–plus: +1
Gamma: 0
What is the mass, in atomic mass units, or each type of nuclear radiation?
Alpha: 4
Beta–minus: negligible
Beta–plus: negligible
Gamma: 0
What is beta–minus radiation made from?
An electron
What is beta-plus radiation made from?
A positron
What is gamma radiation made from?
Short–wavelength, high–frequency EM wave
Describe the ionising power, speed, and penetrating power of alpha radiation
when does alpha radiation occur
Strong ionising power
Slow speed
Absorbed by paper or a few cm of air
occurs when nuclei have too much mass
Describe the ionising power, speed, and penetrating power of beta-minus radiation
when does it occur
Weak ionising power
Fast speed
Absorbed by ~3 mm of aluminium
occurs when nuclei have too many neutrons
Describe the ionising power, speed, and penetration power of beta-plus radiation
when does this occur
Annihilated by electron – so virtually zero range
occurs when nuclei have too many protons or too few neutrons
Describe the ionising power, speed, and penetrating power of gamma radiation
when does this occur
Very weak ionising power
Speed of light
Absorbed by many cm of lead, or several m of concrete
when nuclei has too much energy
how does intensity of gamma radiation decrease with distance and so what law does it follow
intensity decreases with the square of the distance
according to the inverse square law
Which types of nuclear radiation are affected by magnetic fields?
Alpha and beta because they carry a charge
Gamma radiation isn’t affected by the magnetic field
What is the relationship between penetrating power and ionising power, of radiation? Why?
The penetrating power of radiation decreases with increasing ionising power.
This is because radiation loses energy as it ionises atoms. This means that the higher the ionising power of the type of radiation, the more energy it loses in a given distance, so the shorter its range
What safety procedures should be put in place when doing experiments with a radioactive sources?
Radioactive sources should be kept on a lead lined box when they’re not being used
They should only be picked up using long handled tongs or forceps
Take care not to point them at anyone
Describe the investigation for the penetration of different kinds of radiation in the lab
Measure the background count.
Calculate a count rate.
Subtract this from all your results.
Set up the equipment.
Insert different materials between the source and tube, and record the count rate over a sensible time interval.

How can you get an accurate reading for the background count rate of radiation when investigating kinds of penetration?
Radioactive decay is random, so to get an accurate reading the count needs to be measured over a long enough time interval








