P.7 - Radioactivity

What is activity measured in?

becquerel (Bq)

How do you detect radiation?

Geiger Counter

What is activity?

the rate at which a source of unstable nuclei decays

What is radioactive decay?

the nucleus of an unstable atomic nuclei gives out radiation, so it can become more stable

What is the count rate?

the number of decays recorded each second

Why would a nuclei be unstable?

extra neutrons

extra protons

excess enery

What is an alpha particle?

2 neutron and 2 protons

what is the symbol for an alpha particle?

α

What is a Beta particle?

a high speed electrons ejected from the nucleus as a neutron turns into a proton

What is the symbol for a beta particle?

β

What is a gamma ray?

electromagnetic radiation emitted from the nucleus

What is the symbol for a gamma ray?

γ

What is an atomic number?

the number of protons inside a nucleus

What is the mass number?

the number of protons and neutrons in a nucleus

What is the radius size of an atom?

1 × 10^-10

What is the ratio of nucleus radius and an atom’s radius?

1/10,000

How do atoms become ions?

lose or gain electrons

What is an isotope?

the same number of protons and electrons, but a different number of neutrons

How is an alpha particle represented in an nuclear equation?

₄²He

How is a beta particle represented in a nuclear equation?

_-1⁰e

What did the plum pudding model show?

overall neutral charge

positive and negative charges are equal

electrons are in a sea of positive charge

What did the alpha scattering experiment find out?

most electrons passed through, but some bounced back or went in different directions…

THEREFORE, most of the atom is empty small apart from a small concentrated nucleus in the middle

Which type of radiation has the highest ionising power?

alpha

Which type of radiation has the lowest ionising power

gamma rays

Which type of radiation is the most penetrating?

gamma rays

Which type of radiation is the least penetrating?

alpha

What is radioactive contamination?

unwanted presence of radioactive atoms on other materials

What is irradiation?

exposing an object to nuclear radiation, it doesn't become radioactive

What is the definition of activity?

number of nuclei that decay per second

What is the count rate?

the number of counts per second from a Geiger Counter

What is the definition of a half-life?

the time taken for the count-rate to reduce to half it’s initial value

What is the definition of a half-life?

the time taken for the number of unstable radioactive isotope nuclei to half

What is the definition of a half-life?

the time taken for mass of unstable radioactive isotope nuclei to half

What are the medical uses of nuclear radiation?

the exploration of internal organs and control/destruction of unwanted tissue

What type of radiation is used in exploring internal organs and why?

Gamma - highly penetrative, weakly ionising, short half live (not in body long)

Which types of radiation can be used n controlling/destroying unwanted tissue, and why?

gamma and beta - highly penetrating, high dose, long half-life

What is radiation measured in?

sieverts, Sv

What is nuclear FISSION?

the splitting of large, unstable atomic nucleus

What is nuclear FUSSION?

joining of 2 light nuclei to form a heavier nucleus

Which elements are commonly used in fission reactors?

Uranium-235 and Plutonium-239

What is a moderator in nuclear fission?

slows down fast neutrons, so fission chain reaction doesn’t break down

What do control rods do in nuclear fission?

control the speed of the chain reactions

What are the pros of nuclear fission?

no CO₂ produced

lasts many years

more energy produced per 1kg of fuel

What are the negatives of nuclear fission?

expensive to build

non-renewable

radioactive waste has to be stored

slow start-up time

dangerous