atomic structure

Question 1

what is the plum pudding model and who created it

Answer 1

spheres of positive charge with tiny balls of negative electrons stuck in them J.J Thomson

Question 2

what experiment did rutherford do

Answer 2

fired a beam of alpha particles at a sheet of gold foil

Question 3

what were the results of rutherfords experiment

Answer 3

most particles went through
some deflected more than expected
a few deflected back

Question 4

what did scientists relies after rutherfords experiment

Answer 4

most of the mass must be concentrated
the nucleus must have a positive charge
as most atoms passed they relised most of the atom was empty

Question 5

what did Niels Bohr discover

Answer 5

electrons orbiting the nucleus do at certain distances

Question 6

what did james chadwick discover

Answer 6

neutron which explained imbalance between atomic mass and mass number

Question 7

what is the atomic number

Answer 7

number of protons

Question 8

what is the mass number

Answer 8

number of protons and neutrons

Question 9

what are isotopes

Answer 9

are atoms with the same number of protons but a different number of neurons

Question 10

what is ionising radiation

Answer 10

radiation that knocks electrons off atoms creating positive ions

Question 11

what is ionising power

Answer 11

how easily it can knock off an atom

Question 12

what happens to unstable isotopes

Answer 12

decay into other elements and give out radiation

Question 13

what is an alpha particle

ionising power and how far it penetrates

Answer 13

2 neutrons and 2 protons / helium nucleus

don’t penetrate far and stopped by paper
strongly ionising

Question 14

what is a beta

ionisong power and how far it penetrates

Answer 14

a fast moving electron released by nucleus

absorbed by aluminium and moderate ionising

Question 15

what happends to the neutron and proton when beta particle is released

Answer 15

for every beta emitted a nuetron turns into a proton

Question 16

what is gamma

ionising power and how far it penetrates

Answer 16

waves of electromagnetic radiation

penetrate far and stopped by lead
weak ionising

Question 17

how is radioactivity measured

Answer 17

geiger-muller tube

Question 18

what is half life

Answer 18

time it takes for the amount of radiation emitted by a source to half

Question 19

what is the activity of a radioactive source

Answer 19

rate at which a source decays measured in Bq(becquerels)

Question 20

what does short half life mean

Answer 20

activity falls quickly as nuclei is very unstable and decay fast

they are dangerous because of high radiation but quickely become safe

Question 21

what does long half life mean

Answer 21

activity falls slowely

source just sits there releasing a small amount of radiation so very dangerous

Question 22

how do you measure half life of a graph

Answer 22

finding the time interval on the bottom axis corresponding to a halving of the activity

Question 23

which three places does background radiation come from

Answer 23

naturally occurring unstable isotopes
space
human activity

Question 24

what is irradiation

Answer 24

exposure to radiation

Question 25

how do you decrease the amount of irradiation

Answer 25

lead-lined boxes and standing behind barriers

Question 26

what is contamination

Answer 26

radioactive particles getting into objects

Question 27

how do you stop contamination

Answer 27

gloves and tongs

Question 28

what radiation is most dangerous on the out side and why

Answer 28

beta and gamma because they can penetrate to the organs (irradiation)

Question 29

why is alpha not as dangerous outside the body

Answer 29

does not penetrate skin

Question 30

what radiation is most dangerous inside the body and why

Answer 30

alpha as it does damage in a localised area

Question 31

why are beta and gamma less dangerous inside the body

Answer 31

beta is absorbed over a wide area and gamma just passes out

Question 32

what are the risks of radiation

Answer 32

enter living cells and ionise there atoms

lower dose can cause minor damage like giving rise to mutant cells which then divide uncontrollable(cancer)

higher doses kill

Question 33

how is gamma used in medical tracers

Answer 33

gamma isotopes are injected into people and their progress around the body can be traced using an external detector.

A computer converts the reading to a display showing where strongest reading is from

Question 34

why is gamma used in medical tracers

Answer 34

passes straight through

Question 35

what is radiotherapy

Answer 35

gamma rays are directed carefully and at the right dosage to kill the cancer cell

Question 36

what is fission

Answer 36

release of energy from large atoms by splitting them into smaller atoms

Question 37

what is the process of fission

Answer 37

neutron hits the atom splitting into two lighter elements that are the same size

2 or 3 neutrons are released and if moving slowly anougth they are absorbed and cause a chain reaction

Question 38

where does the energy come from in fission

Answer 38

energy in gamma and kinetic energy stores of the free neutrons

Question 39

how are the chain reactions controlled in fission

Answer 39

control rods that are lowerd and raised inside a nuclear reactor to absorb neutrons

Question 40

what is fusion

Answer 40

joining small nuclei

Question 41

process of fusion

Answer 41

2 light nuclei collide at high speed and fuse to create a larger heavier nucleus

the heavier nucleus produced does not have as much mass as some is converted into energy

Question 42

what releases more energy fusion or fission

Answer 42

fusion

Question 43

why is fusion so hard and expensive to build

Answer 43

high temp and pressure