Physics- Atomic structure

Question 1

What is an isotope

Answer 1

An isotope is an element that has the same number of protons, but different number of neutrons.

Question 2

Alpha particle characteristics

Answer 2

• Are helium nuclei
• Has 2 neutrons and 2 protons
• Don’t penetrate far into materials + are stopped quickly
• can only travel few cm in air + are absorbed by a piece of paper
• Strongly ionising

Question 3

Beta particle characteristics

Answer 3

• A fast moving electron released by the nucleus
• 0 mass and charge of -1
• Penetrate moderately far into materials before colliding
• Range in air of few meter, absorbed by sheet of aluminium
• Moderately ionising

Question 4

Gamma ray characteristics

Answer 4

• Waves of electromagnetic radiation released by the nucleus
• Penetrate far into materials without being stopped
• Travel long distance through air and can be absorbed by thick lead or meters of concrete
• Weakly ionising, they pass through rather than collide with atoms

Question 5

What is a half life?

Answer 5

The time taken for the number of radioactive nuclei in an isotope to halve

Question 6

What are nuclear equations + how are they written

Answer 6

• They are a way of showing radioactive decay by using element symbols
• Written in the form: atom before decay—> atom after decay + radiation emitted
• Total mass and atomic numbers must be EQUAL on bother sides

Question 7

What does alpha decay do to the charge + mass of the nucleus

Answer 7

• Alpha decay DECREASES the charge + mass
• Atomic number reduces by 2
• Mass number reduces by 4

Question 8

What does beta decay do to the charge and mass of the nucleus?

Answer 8

• Beta decay INCREASES the charge but the mass STAYS THE SAME
• a neutron in the nucleus turns into a proton + releases a fast moving electron (the beta particle)
• Number of protons in the nucleus has increased by 1 - increasing the + charge (atomic number)
• lost electron and gained proton- mass doesn’t change.

Question 9

What do gamma rays do to the charge + mass of the nucleus?

Answer 9

• Gamma rays DON’T CHANGE the charge or mass
• way of getting rid of excess energy
• no change to atomic mass or atomic number

Question 10

What is background radiation?

Answer 10

• Background radiation is the low-level radiation that’s around us all the time
• You should always measure and subtract the background radiation from your results

Question 11

What are the sources of background radiation?

Answer 11

• Radiation from space- cosmic rays- from the sun. Earths atmosphere protects us.
• Radiation of naturally occurring unstable isotopes
• Radiation due to human activity

Question 12

What is irradiation?

Answer 12

• Something is irradiated when it’s been exposed to a radioactive source
• Irradiating something doesnt make it radioactive

Question 13

What is contamination?

Answer 13

• When unwanted radioactive atoms get onto or into an object
• Contaminating atoms might then decay, releasing radiation which could cause harm
• Wear protective gear and use tongs when handling sources

Question 14

What is the seriousness of each source outside the body?

Answer 14

• Beta and gamma most dangerous - both can penetrate the body and get to the delicate organs
• Alpha is less dangerous- can’t penetrate the skin- easily blocked by small gap of air

Question 15

What is the seriousness of each source inside the body?

Answer 15

• Alpha is most dangerous- highly ionising- do all damage in localised area
• Beta is less dangerous- moderately ionising- radiation absorbed over wider area
• Gamma lest dangerous- leat ionising- mostly pass straight out

Question 16

What are nuclear radiations used for in medicine?

Answer 16

• exploration of internal organs
• control or destruction of unwanted tissue (eg radiotherapy)

Question 17

What type of radioactive source is usually used in medical tracers?

Answer 17

• Gamma
• The radiation passes out of the body without causing too much ionisation
• Should have short half-life so radioactivity inside patient disappears quickly

Question 18

What is a perceived risks

Answer 18

how risky a person thinks something is
(not the same as the actual risk of a procedure)

Question 19

What can a tracer be used for and what is the risk

Answer 19

• used to detect life-threatening conditions (positive)
• risk of cancer us very small (negative)
• In this case the positive outweighs the small risk

Question 20

What is nuclear fission

Answer 20

Type of nuclear radiation used to release energy from large and unstable atoms by splitting them into smaller atoms.

Question 21

What does nuclear fission release?

Answer 21

Two new lighter elements + two or three neutrons

Question 22

What is nuclear fusion

Answer 22

• the opposite of nuclear fission
• when two light nuclei collide at high speed and join (fuse) to make larger, heavier nucleus
• Releases a lot of energy
• Found in fusion reactors which are hard and expensive to build