Basic Ideas About The Atom - Isotopes and radioactivity

Question 0

What is the numerical tendency associated with isotopic masses.

Answer 0

They have masses very close to whole numbers so are written as such.

Question 1

How do isotopes differ from their parent element?

Answer 1

They have a different mass number due to having more or less neutrons in the nucleus.

Question 2

What is the numerical tendency of relative atomic mass?

Answer 2

They are rarely whole number as the R.A.M is a weighted average of the relative isotopic mass.

Question 3

What are the three isotopes of Hydrogen and their properties.

Answer 3

Protium (symbol H). - a single proton

Deuterium (symbol D) - one neutron and one proton

Tritium (symbol T) - two neutrons one proton and is radioactive.

Question 4

Name the three common isotopes of Carbon.

Answer 4

Carbon-12

Carbon-13

Carbon-14

Question 5

What is the main use of carbon-12.

Answer 5

Used as a standard in mass determinations.

Question 6

What is the main use of carbon-14

Answer 6

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.

Question 7

What makes a isotope radioactive ?

Answer 7

This depends on the proton-neutron ratio in the nucleus. If it is too low or too high radioactivity results.

Question 8

How may a radioactive isotope “change”?

Answer 8

It can change by emitting an alpha or beta particle. Through which process gamma rays are also emitted.

Question 9

What is an alpha particle?

Answer 9

An alpha particle is the nucleus of a helium atom.

4
He
2

Question 10

What happens when an alpha particle is emitted.

Answer 10

The mass number goes down by 4 and the atomic number decreases by 2

Question 11

What is the penetration ability of an alpha particle?

Answer 11

They can penetrate 0.01mm of metal.

Question 12

What affects alpha and beta particles

Answer 12

Electric and magnetic fields.

Question 13

What forms a beta particle?

Answer 13

These a created through neutron decay whereby a neutron decays to form an electron and a proton.

Question 14

What happens to the isotope when a beta particle is formed?

Answer 14

The atomic number increases by one as there is a new proton in the nucleus. This changes the atoms species.

Question 15

What is the penetration ability of a beta particle?

Answer 15

It can penetrate 0.01m of metal.

Question 16

What are gamma rays?

Answer 16

High energy (frequency) Electro-magnetic waves.

Question 17

What direct damage do these high energy emissions cause to a cell?

Answer 17

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.

Question 18

How is damage commonly caused to D.N.A by radiation?

Answer 18

This either occurs directly, or because water molecules are split to form ions or radicals which attack the D.N.A

Question 19

What is another means of transmission of radioactive isotopes.

Answer 19

Through inhaling radioactive gasses present in the air where the skin can’t prevent entry of alpha particles.

Question 20

What can the the rate of radioactive decay altered by?

Answer 20

Nothing. It depends upon the isotope and the quantity of that isotope.

Question 21

What is a half life?

Answer 21

The time for the mass of a sample of a radioactive isotope to fall by half.

Question 22

How is radioactivity used to cause cancer?

Answer 22

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.

Question 23

What other medical uses are there of radiation?

Answer 23

Surgical instruments can be sterilised more efficiently with radiation than by temprature.

Question 24

What is the half life of carbon 14?

Answer 24

5730 years.

Question 25

What is carbon 13 used for?

Answer 25

NMR- Nuclear magnetic resonance spectroscopy.

Question 26

What isotope is looked at for radio carbon dating rocks and what is its half life?

Answer 26

Potassium-40

1.248x10^9years.

Question 27

How can radioactivity be used in analysis? giving an example.

Answer 27

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.