Atomic Structure and Radioactivity Flashcards

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1
Q

JJ thompson’s plum pudding model

A

Introduced the idea of subatomic particles - the atom is a uniform, positively charged sphere containing electrons in the sphere that were negatively charged, balacing out the energy

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2
Q

Rutherfords Atomic model

A

a small, positively-charged nucleus surrounded by empty space and then a layer of electrons to form the outside of the atom

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3
Q

Rutherford - Bohr model

A

electrons orbit the nucleus in shells (energy levels)

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4
Q

Rutherford’s Gold Foil Experiment

A

Alpha-particles were directed at a thin sheet of gold foil; most passed through the foil, but a few were deflected - this led to the discovery of the atomic nucleus

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5
Q

what is an alpha particle

A

A helium nucleus

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6
Q

radius of an atom

A

1 x 10^-10m

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7
Q

basic structure of an atom

A

positively charged nucleus composed of both protons and neutrons surrounded by shells with electrons

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8
Q

where is the majority of the mass of an atom concentrated

A

the nucleus

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9
Q

How are electrons arranged

A

at different energy levels in different distances from the nucleus.

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10
Q

how can electrons move closer to the nucleus

A

emission of electromagnetic radiation, goes to a lower energy level

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11
Q

how can electrons move further away from the nucleus

A

absorption of electromagnetic radition, moves to a higher energy level.

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12
Q

Mass number

A

protons + neutrons

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13
Q

atomic number (proton number)

A

number of protons in atom. atoms of same element have same number of protons

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14
Q

Element

A

substance made of one type of atom

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15
Q

Isotope

A

atoms of same element with different amount of neutrons

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16
Q

proton relative mass

A

1

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17
Q

neutron relative mass

A

1

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18
Q

electron relative mass

A

approximately 1/2000

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19
Q

Nucleons

A

collective term for protons and neutrons. particles found in the nucleus of atoms.

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20
Q

proton relative charge

A

+1

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21
Q

neutron relative charge

A

0

22
Q

electron relative charge

A

-1

23
Q

how are atoms represented

A

Atomic symbol in the middle.
Mass number (A) in the top left
Atomic number (X) in the bottom left

24
Q

how do atoms turn into positive ions

A

lose electron(s)

25
Q

what were atoms thought of before the discovery of the electrons

A

tiny sphere that could not be divided

26
Q

what did James Chadwick do

A

discovered the existence of neutrons within the nucleus

27
Q

photon

A

Photons are particles that travel through the wide spaces between atoms

28
Q

what does a photon represent

A

a particle representing a quantum of light or other electromagnetic radiation. A photon carries energy proportional to the radiation frequency

29
Q

Energy associated with a single photon equation

A

Energy (E) = Planck’s constant (h) x frequency of radiation (f)

E = hf

30
Q

What substances are said to be radioactive

A

substances that give out radiation from unstable nuclei all the time

31
Q

Radioactive decay

A

Some atomic nuclei are unstable.Radioactive decay happens when the nucleus gives out radiation as it changes to be more stable.

32
Q

Activity is:

A

rate at which a source of unstable nuclei decays.

33
Q

What is activity measured in

A

becquerel (Bq)

34
Q

Count rate is

A

the number of decays recorded each second by a detector

35
Q

example of a count rate detector

A

Geiger-Muller tube

36
Q

3 types of nuclear radiation

A

alpha particle
beta particle
gamma ray

37
Q

alpha particle

A

consists of 2 neutrons and 2 protons, same as a helium nucleus

symbol:α

38
Q

beta particle

A

high speed electron ejected from nucleus as neutron turns into proton

symbol:β

39
Q

gamma ray

A

electromagnetic radiation from the nucleus

symbol:γ

40
Q

properties of alpha particles

A

relative mass - 4
charge is +
helium nucleus
high ionisation
low penetrating power
stopped by paper or skin
short range in air

41
Q

properties of beta particles

A

relative mass - 1/2000
charge is -
medium ionising power
medium penetrating power
stopped by aluminium
medium range in air

42
Q

properties of gamma rays

A

relative mass - 0
no charge
type of em radiation
low ionisation
high penetrating power
stopped by lead or concrete
very long range in air

43
Q

whats used to represent radioactive decay

A

Nuclear equations

44
Q

Radioactive contamination

A

unwanted presence of materials containing radioactive atoms.

45
Q

hazard of radioactive contamination

A

decay of contaminating atoms would emit radiation

46
Q

Irradiation

A

exposing an object to nuclear radiation. Irradiated object does not become radiaoactive.

47
Q

background radiation is not around us all the time. True or false

A

False, it is

48
Q

natural sources of background radiation

A

rocks and cosmic rays from space

49
Q

man made sources of background radiation

A

fallout from nuclear weapons testing and nuclear accidents

50
Q

level of background radiation is affected by:

A

Occupation and or location

51
Q
A