Radioactivity Flashcards
what are isotopes
forms of an element that have the same number of protons but different numbers of neutrons
how can we tell an atoms nucleus is stable
if it has a certain amount of neutrons for the amount of protons it has
as protons increase, what needs to happen to keep the nucleus stable
more neutrons are needed
what is decay
the process in which unstable atomic nuclei break apart or change, releasing radiation as they do so
what is radiation
energy carried by particles from a radioactive substance
when does an unstable nucleus emit an alpha particle
when it had too few neutrons
what is an alpha particle and what does it do to the element
a helium 4 nucleus, so it decreases the mass number by 4 and the atomic number my 2
when is a beta particle emitted
when the nucleus has too many neutrons
what is a beta particle and how does it change the element
– a high speed electron ejected from the nucleus as a neutron turns into a proton
and it increases the atomic number by 1
when are gamma rays emitted
after emitting an alpha or a beta particle, since the nucleus would be too hot
what are gamma rays
electromagnetic radiation from the nucleus
what is activity
the rate at which a source of unstable nuclei decay
what is activity measured in
Beqerels
Alpha penetrating power
stopped by skin or paper
beta penetrating power
stopped by 3mm aluminium foil
gamma penetrating power
stopped by lead or concrete
alpha ionising power
high - can produce a lot of ions when colliding with a material
beta ionising power
low
gamma ionising power
very low
alpha range in air
less than 5cm
beta range in air
about 15cm
gamma range in air
several meters
how do u measure radioactive decay
using a geiger muller tub
how do geiger muller tubes work
the radiations ionise the gas inside and the charged particles move across the chamber and get counted as charges
what is the half life of a radioactive isotope
the time it takes for the number of nuclei of the isotope in a sample to halve
how do radiation particles differ in terms of electric fields
- alpha and beta particles are deflected in opposite directions in an electric field
- beta particles are deflected more than alpha particles
- because alpha particles have a greater charge than beta but much less mass
what is an ion
a charged particle
what is radioactive decay
the process in which a nucleus becomes stable by giving out radiation
characteristics of radioactive decay
- random and unpredictable
what is the count rate
- the number of decays recorded each second by a detector
what is half life
the time it takes for the number of nuclei of the isotope in a sample to halve
alternative definition for half life
the time it takes for the count rate from a sample containing the isotope to fall to half its initial level
