Basic Ideas About The Atom - Isotopes and radioactivity Flashcards
What is the numerical tendency associated with isotopic masses.
They have masses very close to whole numbers so are written as such.
How do isotopes differ from their parent element?
They have a different mass number due to having more or less neutrons in the nucleus.
What is the numerical tendency of relative atomic mass?
They are rarely whole number as the R.A.M is a weighted average of the relative isotopic mass.
What are the three isotopes of Hydrogen and their properties.
Protium (symbol H). - a single proton
Deuterium (symbol D) - one neutron and one proton
Tritium (symbol T) - two neutrons one proton and is radioactive.
Name the three common isotopes of Carbon.
Carbon-12
Carbon-13
Carbon-14
What is the main use of carbon-12.
Used as a standard in mass determinations.
What is the main use of carbon-14
Used in the carbon dating system where the ratio of carbon-12 to carbon-14 and as carbon-14 is unstable you can calculate the number of past lives that have occurred.
Only works on plant matter.
What makes a isotope radioactive ?
This depends on the proton-neutron ratio in the nucleus. If it is too low or too high radioactivity results.
How may a radioactive isotope “change”?
It can change by emitting an alpha or beta particle. Through which process gamma rays are also emitted.
What is an alpha particle?
An alpha particle is the nucleus of a helium atom.
4
He
2
What happens when an alpha particle is emitted.
The mass number goes down by 4 and the atomic number decreases by 2
What is the penetration ability of an alpha particle?
They can penetrate 0.01mm of metal.
What affects alpha and beta particles
Electric and magnetic fields.
What forms a beta particle?
These a created through neutron decay whereby a neutron decays to form an electron and a proton.
What happens to the isotope when a beta particle is formed?
The atomic number increases by one as there is a new proton in the nucleus. This changes the atoms species.
What is the penetration ability of a beta particle?
It can penetrate 0.01m of metal.
What are gamma rays?
High energy (frequency) Electro-magnetic waves.
What direct damage do these high energy emissions cause to a cell?
They break chemical bonds in the cells molecules giving rise to cell death at high doses or reduced growth rates. And at lower doses they cause mutations and the formation of cancerous cells.
How is damage commonly caused to D.N.A by radiation?
This either occurs directly, or because water molecules are split to form ions or radicals which attack the D.N.A
What is another means of transmission of radioactive isotopes.
Through inhaling radioactive gasses present in the air where the skin can’t prevent entry of alpha particles.
What can the the rate of radioactive decay altered by?
Nothing. It depends upon the isotope and the quantity of that isotope.
What is a half life?
The time for the mass of a sample of a radioactive isotope to fall by half.
How is radioactivity used to cause cancer?
Cancer cells can be destroyed by radioactivity. A cobalt-60 source is used to irradiate cancer patients. The dose is carefully calculated so that only cancer cells are destroyed.
What other medical uses are there of radiation?
Surgical instruments can be sterilised more efficiently with radiation than by temprature.
What is the half life of carbon 14?
5730 years.
What is carbon 13 used for?
NMR- Nuclear magnetic resonance spectroscopy.
What isotope is looked at for radio carbon dating rocks and what is its half life?
Potassium-40
1.248x10^9years.
How can radioactivity be used in analysis? giving an example.
The mechanism of a reaction can be followed by identifying a radioactively labelled atom through a series of changes. E.g radioactive phosphorus can be used to see what happens to phosphorus in green plants.
