atomic structure Flashcards
What did John Dalton’s ideas in 1804 consist of?
Matter was made up of tiny spheres (atoms) and each element was made up of a different type of ‘atom’.
What did JJ Thompson’s model of the atom consist of?
Plum Pudding Model: Discovered electrons and suggested atoms were spheres of positive charge with small negative electrons within it.
What did scientists realise from Rutherford’s Alpha Scattering Experiment in 1909?
That most of an atom’s mass was concentrated in a central nucleus.
What did Niels Bohr say an atom’s nucleus was made up of?
A group of protons with the same positive charge.
Who proved the existence of the electron in 1932?
James Chadwick.
What is the nucleus made up of in the current model of the atom?
Protons with a 1+ charge and neutral neutrons.
What is an isotope?
Atoms of the same element with the same number of protons but a different number of neutrons.
What is radioactive decay?
When unstable isotopes decay into other elements and give out radiation as they try to become stable.
What is ionising radiation?
Radiation that knocks electrons off atoms, creating positive ions.
What is an alpha particle made up of?
Two neutrons and two protons.
What is an alpha particle also known as?
A helium nucleus.
How far can alpha particles travel in air?
A few centimetres.
What are alpha particles absorbed by?
A sheet of paper.
How ionising are alpha particles?
Strongly ionising.
What are beta particles?
High speed electrons.
How ionising are beta particles?
Moderately ionising.
How far can beta particles travel in air?
A few metres.
What are beta particles absorbed by?
A 5mm thick sheet of aluminium.
For every beta particle emitted…
A neutron in the nucleus turns into a proton.
What are gamma rays?
Waves of electromagnetic radiation with a short wavelength.
How far do gamma particles travel in air?
Long distances.
How ionising are gamma particles?
Weakly ionising but damaging.
What are gamma particles absorbed by?
Thick lead sheets.
What is the nuclear equation?
Atom before decay—> atom(s) after decay + radiation emitted.
What does alpha decay do?
Decreases the charge and the mass of the nucleus.
What does beta decay do?
Increases the charge of the nucleus.
What is radiation measured by?
A Geiger muller tube and counter.
What is activity measured in?
Becquerels, (Bq)
What is a half life?
The time taken for the number of radioactive nuclei in an isotope to halve.
What is background radiation measured in?
Sieverts (Sv).
What does irradiation mean?
Exposure to radiation.
What does contamination mean?
Radioactive particles getting onto objects.
Why are alpha sources dangerous inside the body?
They do all their damage in a very localised area.
Why are beta and gamma rays dangerous outside the body?
They can penetrate the body and potentially reach delicate organs.
What are gamma rays used for in medicine?
~Medical tracers
~Radiotherapy
What are risks do using radiation medically?
~Possible radiation sickness
~Radiation can enter living cells and cause tissue damage
~Lower doses could give rise to cancers
What is nuclear fission?
The splitting of a large, unstable nucleus.
What is nuclear fission used for?
Releasing energy from large, unstable atoms by splitting them into smaller atoms.
What is formed in nuclear fission when atoms split?
~2 lighter and roughly the same size elements
~Two or three neutrons are released
What causes a chain reaction in nuclear fission?
When a neutron is moving slowly enough to be absorbed by another nucleus.
What is nuclear fusion?
When two light nuclei collide and fuse together to make a larger, heavier nucleus.
