Atomic structure and radioacticity Flashcards
What is the radius of an atom?
……….-10…..
1 x 10…..m..
What is the radius of the nucleus?
It is less than 1 / 10 000 of the radius of the atom.
Do energy levels further away from the nucleus have more or less energy?
HIGHER energy than those which are CLOSER to the nucleus.
What is an isotope?
They are atoms of the same element with a different number of NEUTRONS.
What is a alpha particle?
The same as a HELIUM NUCLEUS (two protons joined to two neutrons).
What is a beta particle?
An ELECTRON which is EJECTED from the nucleus at very high speed.
What do some isotopes have?
An UNSTABLE nucleus.
How do unstable isotopes become stable?
The nucleus gives out RADIATION (RADIOACTIVE DECAY).
What is meant by activity?
The rate at which a sourece of unstable nuclei decay.
What is activity measured in?
Becquerel (Bq) 1 Bq = 1 decay per second.
What can we use to measure activity?
Geiger-Muller tube.
What happens in beta decay?
A NEUTRON changes into a PROTON and an ELECTRON.
What is gamma radiation?
Gamma rays are a type of ELECTROMAGNETIC RADIATION from the nucleus.
What are alpha particles stopped by?
A single sheet of paper.
What are beta particles stopped by?
A FEW MILLIMETRES OF ALUMINIUM.
What is gamma radiation stopped by?
SEVERAL CENTIMETRES OF LEAD.
What can cause radiation to form ions?
When radiation COLLIDES with atoms. (causing atoms to lose electrons forming ions)
How ionising are alpha particles?
VERY STRONGLY IONISING.
How ionising are beta particles?
QUITE STRONGLY IONISING.
How ionising is gamma radiation?
WEAKLY IONISING.
What two rules are there for alpha decay?
1) The ATOMIC NUMBER DECREASES BY 2.
2) The MASS NUMBER DECREASES BY 4.
Whats the rule for beta decay?
The ATOMIC NUMBER INCREASES BY 1 but the mass number does not change.
How can scientists predict when a nucleus will decay?
The can’t, decay is a RANDOM process.
What is meant by half-life?
It is the time it takes for the number of NUCLEI of the isotope in a sample to HALVE.
What is Irradiation?
Exposing an object to NUCLEAR RADIATION (alpha, beta, gamma or neutrons).
Give one use gamma radiation?
Sterilisation of objects.
What is radioactive contamination?
When UNWANTED RADIOACTIVE ISOTOPES end up on other materials.
