Radioactivity

Question 1

Plum pudding model

Answer 1

Thompson suggested that atoms were spheres of positive charge with tiny negative electrons stuck in them

Question 2

Rutherford’s model

Answer 2

They fired alpha particles through a gold sheet.
Most particles went straight through
Some were deflected
Few were deflected the way they came
Most of the mass is a the centre
Atom is empty space
Nucleus is positive as it repelled positive alpha particles

Question 3

Current model of an atom

Answer 3

An atom is a positively charged nucleus surrounded by negatively charged electrons

Question 4

what happens in beta plus decay?

how does it affect the mass number and atomic number?

Answer 4

a proton changes into a neutron and a positron
it does not change the mass number
the atomic number decreases by one as it has one less proton

Question 5

what happens in beta minus decay?

how does it affect the mass number and the atomic number?

Answer 5

a neutron changes into a proton and an electron
the mass number doesn’t change
the atomic number increases by 1 as it has one more proton

Question 6

what happens in alpha decay?

how does it affect the mass number and atomic number?

Answer 6

it loses two neutrons and two protons
the mass number decreases by 4
the atomic number decreases by 2

Question 7

what happens when a neutron emits a neutron?

Answer 7

the mass number decreases by 1

the atomic number stays the same

Question 8

what is the alpha sign?

Answer 8

x 4 at top 2 at bottom

Question 9

what is the beta minus sign?

Answer 9

B 0 at top -1 at bottom

Question 10

what is the positron sign?

Answer 10

B 0 at top 1 at bottom

Question 11

what is the neutron sign?

Answer 11

n 1 at top 0 at bottom

Question 12

do gamma rays change the charge or mass of the nucleus?

Answer 12

the mass and atomic number stay the same

Question 13

what is an atom?

Answer 13

a positively charged nucleus, consisting of protons and neutrons, surrounded by negatively charged electrons, . all of the mass is in the nucleus

Question 14

what do the shells in an atom show?

Answer 14

the energy levels

Question 15

what happens to an inner electron if it absorbs electromagnetic radiation?

Answer 15

can move up to a higher level- when it does move up I moves to an empty or partially filled shell

Question 16

what then happens when the electron has moved shells?

Answer 16

it will quickly fall back to its original energy level, and will emit the energy it absorbed- which will be carried away by em radiation

Question 17

how do atoms form positive ions when they lose an electron?

Answer 17

if an outer election absorbs enough energy it can leave the atom - It is now a free electron and the atom has been ionised
the atom is positive because it has more protons than electrons

Question 18

what is an isotope?

Answer 18

are atoms of the same element with the same number of protons but a different number of neutrons

Question 19

what is an Alpha particle?

Answer 19

two neutrons two protons

they are strongly ionising

Question 20

what can stop alpha particles?

Answer 20

few cm of air and thin piece of paper

Question 21

what is a beta minus particle?

Answer 21

a fast moving electron

moderatley ionsing

Question 22

what is a beta plus particle?

Answer 22

a fast moving proton

moderatley ionisng

Question 23

what can stop beta minus particles?

Answer 23

few metres of air and a sheet of 5mm thick aluminium

Question 24

what are gamma rays

Answer 24

em radiation

weakly ionising

Question 25

what can stop gamma rays?

Answer 25

thick sheets of lead and metres of concrete

Question 26

what is background radiation?

Answer 26

the low level of radiation that is around us all the time?

Question 27

how does radiation come from space?

Answer 27

radiation from space is known as cosmic rays. it comes from the sun but the earths atmosphere protects us from lots of this radiation

Question 28

Irradiation

Answer 28

objects near a radioactive source are irradiated by it - they are exposed to it

Question 29

What can you do to reduce the effects of irradiation?

Answer 29

keep sources in a lead lined box, stand behind barriers or being in a different room

Question 30

contamination

Answer 30

radioactive particles getting onto objects

Question 31

What can you do to avoid contamination?

Answer 31

gloves and tongs to avoid getting it on you

Question 32

what do medial people do to avoid the effects of irradiation?

Answer 32

they wear a photographic film badge to monitor their exposure

Question 33

what do industrial workers wear to protect themselves from contamination?

Answer 33

they wear protective suits to stop them breathing In particles

Question 34

What can radiation do?

Answer 34

can enter living cells and ionise atoms and molecules within them - tissue damage

Question 35

what can a lower dose of ionisation do?

Answer 35

it can cause minors damage without killing cells- this can give a rise to mutant cells that divide uncontrollably which is called cancer

Question 36

what can a high dose of ionisation do?

Answer 36

tends to kill cells completely, causing radiation sickness

Question 37

how do hospitals prevent staff and patients from too much radiation?

Answer 37

shielding is used to protect staff and untreated body parts of patients

Question 38

What does activity mean in decay?

Answer 38

the rate at which a source decays - it is measured in becquerels Bq - 1 decay per second

Question 39

what is the half life of a radioactive isotope?

Answer 39

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

Question 40

what does a short half life tell you about the activity?

Answer 40

that its activity falls quickly because the nuclei are very unstable and rapidly decay

Question 41

what does a long half life tell you about the activity?

Answer 41

the activity falls more slowly because most of the nuclei won’t decay for a long time