atomic structure

Question 1

how does radiation in smoke detectors work?

Answer 1

-alpha radiation used in smoke detectors
-this ionises the air causing current to flow
-when air has smoke, it absorbs/ stops alpha current is broken = alarm

Question 2

what is an isotope?

Answer 2

-atoms of same element with different number of neutrons

Question 3

what is radioactive decay?

Answer 3

-process of emitting high energy particles or waves from unstable nucleus
-process of emitting radiation

Question 4

what is irradiation?

Answer 4

-process of exposing material to alpha, gamma, or beta radiation
-to sterilise equipment to kill microorganisms
-to sterilise food, makes it last longer

Question 5

what is contamination?

Answer 5

-unwanted radioactive isotope leaking onto material
-much more harm potential, due to continuous radioactive exposure it will produce

Question 6

changes to atom structure after:
-alpha decay
-beta decay
-gamma decay

Answer 6

-alpha: mass no. decreases by 4, atomic no. decreases by 2
new element created
-beta: only change, atomic number +1 (neutron changes to proton and an electron, elec is emitted, proton remains.)

Question 7

half life:

Answer 7

rate at which activity of radioactive material halves.
-time taken for half of nuclei of sample of radioactive isotope to decrease by half

Question 8

what causes atomic nuclei to become unstable?

Answer 8

-because they are too large
-too many or too few neutrons
-imbalance of forces between particles in nucleus

Question 9

what is activity?

Answer 9

rate at which instable nuclei decay

Question 10

what is count rate?

Answer 10

rate at which radioactive emissions detected

Question 11

what happens when electrons absorb EM radiation?

Answer 11

they move to higher energy levels,
-causes atom to be unstable
-to return to original energy level, it moves back down, and emits EM radiation.

Question 12

when are electrons knocked out of atom?

Answer 12

-objects rubbed together, elec removed by friction
-elec can absorb EM radiation to gain enough energy to leave atom
-from chemical reactions

Question 13

prevention of damage from:
-irradiation
-contamination

Answer 13

-IR: lead lined suit, lead absorbs radiation
-CON: air tight suits when working in area that may have radiation leak, prevents atoms getting inside body

Question 14

what is a dose? how is it measured?

Answer 14

-a dose is amount of radiation received by a person
-measured in sieverts (Sv)
-one Sv is very big
normal dose of person per year: 3mSv (0.003 Sv)

Question 15

what is a bequerel:

Answer 15

measurement of amount of radiation emitted by source every second

Question 16

what is counts per second:

Answer 16

number of decays per second????

Question 17

two ways of nuclear fission

Answer 17

-spontaneously
fission is unforced and happens by itself (very rare)

-absorbing a neutron
can split a nucleus by making it even less stable

Question 18

name two nuclear fuels

Answer 18

uranium-235, plutonium-239

Question 19

steps of nuclear fission

Answer 19

-slow moving neutron fired at a large unstable nuclei
-breaks into two smaller nuclei, and two/three neutrons
-energy prod in the form of gamma radiation
-if neutrons slow enough to be absorbed by other large unstable nuclei, chain reaction happens

Question 20

what is the energy prod from fission used for

Answer 20

to heat water and prod steam, which can drive turbines connected to an electricity generator

Question 21

pros and cons of nuclear energy

Answer 21

PROS
-U and Pu are cheap
-prod a large and steady amount of energy
-clean; doesn’t prod GH gases
CONS
-power plants, very expensive to build
-nucl waste expensive to get rid of
-risk of major disaster

Question 22

process of nuclear fusion

Answer 22

-two light nuclei collide at high speeds to prod a heavier nucleus (ex. hydrogen > helium)
-heavier nucleus has less mass than the two separate nuclei, as some mass converted to energy
-creates a lot more energy than fission
-not used to make energy for us as it requires rlly high press & temp
-happens in stars

Question 23

why does fusion only happen at very high temperatures and pressures?

Answer 23

to overcome the repulsion of the positively charged nuclei

Question 24

a substance is radioactive when it consists of

Answer 24

unstable isotopes that can decay

Question 25

describe an alpha particle

Answer 25

-2 protons & 2 neutrons, represented by a helium nucleus
-has charge of 2+
-relatively large, so only travel a few cm and absorbed by paper
-strongly ionising, so can knock electrons off of any atoms they collide w/

Question 26

describe a beta particle

Answer 26

-an electron
-no mass
-charge of 1-
-one of the neutrons in the nucleus decays as a proton and electron, proton stays in nucleus and electron emitted at high speed
-tiny so moderately ionising and penetrating

Question 27

describe gamma rays

Answer 27

-waves of electromag radiation
-often emitted after alpha or beta radiation
-no mass or charge, so pass right through materials
-not very ionising
-stopped by thick lead/concrete

Question 28

describe neutron radiation

Answer 28

if a nucleus has too many neutrons and is unstable, it emits neutrons

Question 29

for a beta decay equation, the atomic mass (top num.) ……….. and the atomic num ……

Answer 29

-stays the same
-increases by 1

Question 30

half life can be defined as

Answer 30

• the time taken for the number of radioactive nuclei in a sample to halve
• the time taken for the number of decays or activity to half

Question 31

what is meant by radioactive activity

Answer 31

overall rate of decay of all isotopes in sample

Question 32

what is irradiation

Answer 32

the process by which objects are exposed to radiation

Question 33

what makes ionizing radiation dangerous

Answer 33

• can enter living cells and interact with the molecules inside
• can ionize DNA causing mutations

Question 34

What factors affect the dosage of radiation

Answer 34

• how far from the source you are
• how long you’re exposed
• how radioactive the substance is

Question 35

how are medical tracers used in radiation medicine

Answer 35

gamma rays are used
patients are made to swallow radioactive isotope
-movement of isotope is traced in the body to see if organs are working properly and are absorbing the right amount of isotope etc.
- only use isotopes with short half lives

Question 36

what type of radiation is used for an internal and external treatment

Answer 36

external is gamma
internal is beta

Question 37

Exposure to low levels of radiation over long periods can lead to cancer.

Why is this?

Answer 37

Radiation can cause mutations in our DNA…
…which may cause our cells to divide uncontrollably