Chapter 8 - Radioactivity

what is radioactivity?

the spontaneous breaking up of unstable nuclei with the emission of one or more types of radiation

what are the 3 types of radiation?

• alpha particles

• beta particles

• gamma radiation

what structure does an alpha particle have?

2 nucleus and 2 protons (same as a helium nucleus)

what type of radiation can be represented as ⁴₂He ?

alpha particles

what type of charge does an alpha particle carry?

double positive charge

why are alpha particles slow moving?

because they have a large mass

what are the origins of alpha particles?

they are released (thrown out) from unstable nucleus so it may become more stable

why can alpha particles not pass through a sheet of paper?

they have low penetrating power

what are beta particles?

fast-moving electrons

what type of radiation can be represented as ⁰_-1 e ?

beta particles

what is the origin of beta particles?

formed when a neutron in an unstable nucleus is converted to a proton and electron. The beta particle is ejected from the nucleus

why are beta particles faster moving than alpha particles?

they have a smaller mass

what material can stop a beta particle?

a 5mm of aluminium

what is gamma radiation?

high-energy electromagnetic radiation

what speed does gamma radiation travel at?

speed of light

what is different about gamma radiation from other 2 types?

does not consist of charged particles and are not deflected in magnetic or electric fields

what is the origin of gamma radiation?

unstable nucleus emits gamma radiation to lose surplus energy

how much penetrating power does gamma radiation have?

extremely high

what material can stop gamma radiation?

thick slab of lead

how dangerous is gamma radiation?

most dangerous of 3 radiation types

if absorbed can cause cancer

what is a use of gamma radiation?

radio therapy for cancer patients

what is a nuclear reaction?

a process that alters the composition, structure or energy of an atomic nucleus

compare a chemical and nuclear reaction

chemical reaction

• involves electrons rather than nucleus

• no new element formed

• no release of nuclear radiation

• chemical bonds broken and formed

nuclear reaction

• changes take place in nucleus and electrons not involved

• new element formed

• release of nuclear radiation

• no chemical bond breaking or forming involved

what happens when an atom loses a beta particle?

new element formed has one less neutron and one more proton.

mass number stays same, atomic number increases by 1

what happens when atoms lose gamma radiation?

energy lost from nucleus but does not give rise to new elements

what is transmutation?

the changing of one element to another

what is the half-life of an element?

the time taken for half of the nuclei in any given sample to decay

how is half-life measured?

geiger-muller tube and ratemeter

do temperature and pressure effect the half-life of an element?

no

what is an archaeological use of radioactivity?

radiocarbon dating

what is the half-life of Carbon-14?

5730 years

what is radiocarbon dating?

a technique used to determine the age of an object containing carbon. It is based on ratio of carbon-14 to carbon-12 in the object

by what type of radiation does carbon-14 decay?

beta radiation

what are 2 medical uses of radioactivity?

radiotherapy and sterilising medical instruments

what is radiotherapy?

use of gamma rays to penetrate the body and kill cancerous cells.