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1.2 basic ideas about atoms Flashcards

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1
Q

what is an isotope?

A

an atom of an element with the same number of protons, but different number of neutrons

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2
Q

what makes a nuclei to become unstable?

A

when isotopes of elements are formed that contain too many neutrons, it makes the nucleus ‘heavy’ and unstable

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3
Q

what happens when a nuclei becomes unstable?

A

radiation is emitted from the nucleus of that atom which results in the formation of a new atom

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4
Q

the heavier the atom, the ____ likely it is to degrade/emit radiation?

A

more

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5
Q

what are the 5 radiation types and decay?

A
  1. alpha
  2. beta
  3. gamma
  4. positron emission
  5. electron capture
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6
Q

what are the properties of alpha? and why?

A
  • same structure as a helium nucleus (2 protons, 2 neutrons)
  • doesn’t have any electrons so has a positive charge if 2+ (so will be affected by an electric field)
  • penetrating power -> easily stopped by a thin sheet of paper so pose no threat to humans when outside the body
  • ionising ability -> their relatively large size makes it easy for them to knock electrons off atoms to form negatively charged ions
  • electric fields -> they are attracted towards the negatively charged plate but deflection is small due to large mass
  • emission -> when emitted by an unstable nucleus, the particle leaves behind a new nucleus (different element) with 2 fewer protons and 2 fewer neutrons
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7
Q

what is the structure of alpha?

A

4 He
2

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8
Q

why does alpha have a positive charge of 2+?

A

because it doesn’t have any electrons

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9
Q

does alpha have a strong or weak penetrating power?

A

weak - it is easily stopped by a thin sheet of paper so pose no threat to humans when outside the body

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10
Q

does alpha have a high or low ionising ability?

A

high - they are highly ionising

their relatively large size makes it easy for them to knock electrons off atoms to form negatively charged ions

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11
Q

in an electric field, what plate is alpha attracted to?

A

towards the negatively charged plate but deflection is small due to large mads

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12
Q

write an equation to represent the emission of an alpha particle from a carbon - 12 nuclei

A

12 C —> 4He + 8 Be
6 2 4

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13
Q

what are the properties of beta?

A
  • formed when a neutron of an unstable element decays to form a proton and an electron (the electron is propelled away at high speed from the nucleus and becomes known as a beta particles)
  • it has a mass of 0 and a charge of -1
  • penetrating power = stopped by a thin sheet of aluminium so are much more dangerous to humans when outside the body
  • ionising ability = ionises less intensely than an alpha particle due to its smaller size
  • electric fields = they are attracted towards the positively charged plate but deflection is larger due to their small mass
  • emission = when a beta particle is emitted, it leaves behind a new nucleus (different element) with 1 more proton so the atomic number increases by 1 and the mass number stays the same
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14
Q

what is the structure of a beta particle?

A

0 e -
-1

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15
Q

how is a beta particle formed?

A

when a nucleus of an unstable element decays to form a proton and an electron. the electron is propelled away at high speed from the nucleus and becomes known as a beta particle

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16
Q

what is the mass and charge of a beta particle?

A

mass 0
charge -1

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17
Q

what is the penetrating power of a beta particle?

A

they are stopped by thin sheets of aluminium so are much more dangerous to humans when outside the body

(stronger than alpha, weaker than gamma)

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18
Q

what is the ionising ability of a beta particle?

A

it ionises much less intensely than an alpha particle due to its size

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19
Q

in an electric field, what plate is a beta particle attracted to?

A

towards the positively charged plate but deflection is large due to their small mass

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20
Q

what are the properties of gamma?

A
  • is emitted by unstable elements in order to release energy
  • does not have a mass as it’s an electromagnetic wave with a very small wavelength and a high frequency and energy
  • penetrating power = it can travel great distances and has a high penetrating power. it will pass directly through the human body. it can be stopped by very thick lead
  • ionising ability = having no mass, it can only weakly ionise
  • electric fields = having no charge it is not deflected by electric fields
  • emission = it doesn’t change the structure of the nucleus from which it is emitted, it just reduces the amount of energy contained within
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21
Q

what is the structure of gamma? (charge, mass)

A

0 Y
0

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22
Q

how is gamma radiation emitted?

A

by unstable elements in order to release energy

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23
Q

why doesn’t gamma have a mass?

A

bc it is an electromagnetic wave with a very small wavelength and a high frequency and energy

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24
Q

what is the penetrating power of gamma?

A

it can travel great distances and has a high penetrating power. it will pass directly through the human body. it can be stopped by very thick lead

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25
Q

what is the ionising ability of gamma?

A

because it has no mass, it can only weakly ionise

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26
Q

in an electric field, what plate is gamma attracted to?

A

because it doesn’t have a charge, it is not deflected by electric fields

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27
Q

when emitted, how does gamma change the structure of the nucleus?

A

it doesn’t change the structure of the nucleus from which it is emitted, it just reduced the amount of energy contained within

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28
Q

what is a positron?

A

the opposite particle to an electron

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29
Q

what does positron emission result in?

A

the process of a proton turning into a neutron
(there is no change in mass number)

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30
Q

what is the structure of a positron?

A

0 e +
+1

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31
Q

what is electron capture?

A
  • it pretty much uses the same principles of beta emission
  • an electron can be ‘captured’ by an atom
  • there is no change in mass number. a proton changes to a neutron
  • beta particle add to an atom

23Na + 0 e —> 23Ne
11 -1 10

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32
Q

explain the deflection (of alpha, beta and gamma through an electric field)

A
  • alpha radiation is deflected towards the negative plate
  • beta radiation is deflected towards positive plate
  • gamma radiation travels straight through as unaffected by charge
  • beta radiation deflects at a greater angle and meets plate earlier than alpha
  • beta particles charged and lighter, can be deflected more easily than alpha which are charged but heavier
  • gamma radiation has no associated mass (electromagnetic wave)
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33
Q

why is alpha radiation deflected towards the negative plate in an electric field?

A

because it has a positive charge

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34
Q

why is beta deflected towards the positive plate in an electric field?

A

because it has a negative charge

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35
Q

why does gamma radiation travel straight through in an electric field?

A

is is an electromagnetic wave so is unaffected by charge

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36
Q

why does beta radiation deflect at a greater angle and meet the plate earlier than alpha in an electric field?

A

beta particles are charged and lighter, so can be deflected more easily than alpha which are charged but are heavier

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37
Q

half-life definition

A

the time taken for the mass of a radioactive isotope to decay by half

OR

the time taken for half of the atoms of a radioactive sample to decay

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38
Q

what is the relationship between the rate of decay to the number of atoms present in the sample? why?

A

proportional
bc since half-life is unchanging

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39
Q

why does the actual rate of decay slow down as time passes?

A

since it is proportional to the number of unstable nuclei in the sample

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40
Q

will the radioactivity of radioactive isotopes ever fall to zero?

A

no so radioactive isotopes must be disposed of with care

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41
Q

how long would it take a radioactive substance to reduce to 1/8th of its original value if its half life was 2 mins?

A

1 -> 1/2 -> 1/4 -> 1/8
3HL = 2mins x 3 = 6 mins

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42
Q

how long would it take a radioactive substance to reduce to 25% of its original value if its half life was 35 years?

A

1 -> 0.5 -> 0.25
2HL = 35 x 2 = 70 years

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43
Q

what are the two ways you can work out half life?

A
  1. from data
  2. from graphs
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44
Q

when reading half life off a graph, what is important to remember?

A

for it to be a true half life graph, each time you do this, the half life must remain constant between readings

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45
Q

what are the uses of radiation in industry?

A

only need 1 but:
- to measure the thickness of paper
- to find leaks in underground pipes
- to preserve food
- in smoke detectors

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46
Q

what is the use of radiation in carbon dating?

A

carbon dating is used to calculate the age of plant and animal remains

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47
Q

what are the uses of radiation in health and medicine?

A

only need 1 but:
- to sterilise surgical instruments
- to treat cancer - cobalt 60 is used to irradiate cancer patients
- in tracer studies - iodine 132 is used to study thyroid activity

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48
Q

up to what element do we need to know the electronic configuration?

A

krypton - 36

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49
Q

what are the three types of orbitals (shells) and how many can each one hold?

A

s, p and d

s can hold 2 electrons
p can hold 6 electrons
d can hold 10 electrons

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50
Q

what does n=1 mean?
what does n=2 mean?

A

n=1 is shell 1
n=2 is shell 2

(‘n’ means principal quantum number - or energy level)

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51
Q

does energy increase as you move away from the nucleus??

I
I
I

A

yes

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52
Q

do energy levels get closer or further away from each other as they get further from the nucleus?

A

they get closer as they get further from the nucleus

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53
Q

what is the full electronic configuration of Titanium - 22?

A

1s^2 2s^2 2p^6 3s^2 3p^6 4s2 3d2

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54
Q

what is the order of filling when working out the electrons of an element?

A

1s
2s
2p
3s
3p
4s
3d
4p
4d

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55
Q

why are electrons placed into the energy levels they are placed in?? why is the 4s sub-energy level filled before the 3d sub-energy level?

A

when electrons are placed into energy levels, they want to occupy those with the lowest energy first

the 4s sub-energy level is of lower energy and nearer the nucleus than the 3d sub-energy level

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56
Q

when doing the ‘arrow in the box method’ what direction do the arrows point?

A

1 has to point up, 1 has to point down

  • in opposite directions
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57
Q

how do you fill ‘the arrow in the box method’? why?

A

fill all the boxes first, then pair them

bc electrons have a negative charge, they stay away from each other for as long as possible

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58
Q

what is the noble gas ‘core’/ shorthand method of electronic configuration?

A

find the noble gas before the element you are working out

write [‘noble gas’] then 3d^8 4s^2 etc

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59
Q

what are the two elements that are the exceptions to the rules for electronic configuration?

A
  1. chromium
  2. copper

they allow one of the 4s electrons to travel to the 3d sub level early as half filled (d^5) and fully filled (d^10) sub shells have a high stability

they are so close to having a half full d sub-energy level that it ‘takes’ one of the 4s electrons to achieve it ‘early’

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60
Q

how can you work out the electronic configuration of ions?

A

it can be deduced by simply adding or removing the appropriate number of electrons

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61
Q

what are the rules that deduce the order in which electrons are removed when working out the electronic configuration of ions?

A
  1. remove outer shell electrons first
  2. remove paired electrons before unpaired electrons in the same sub-level
  3. 4s ELECTRONS ALWAYS GET REMOVED BEFORE 3d
  4. add the appropriate number of electrons if the ion is negatively charged
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62
Q

why do atoms remain on an energy level? (why do they have fixed energy levels?)

A

cause they are quantised

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63
Q

what is the lowest energy level that an atom has? highest?

A

n=1
n= infinite

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64
Q

what do you call the energy level closest to the nucleus? (n=1)

A

the ground state

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65
Q

does energy increase as you go up the energy levels?

A

yes

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66
Q

is there a n=0 level?

A

no

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67
Q

what happens to the difference in energy between energy levels as you go from one level to the next?

A

it decreases

—————
—————

—————

—————

—————

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68
Q

what eventually happens to the energy levels as they go up towards n=infinite?

A

they converge - it becomes impossible to separate out the energy levels
(this limit is called the convergence limit)

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69
Q

what is the convergence limit?

A

the point at which the energy levels converge and become impossible to separate out

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70
Q

will each atom have a slightly different energy at which these levels reside?

A

yes

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71
Q

what represents ionisation of an atom?

A
  • beyond the convergence limit
  • n=1 —> n=infinite

(if an electron passes n=infinite, it looses it and it becomes an ion)

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72
Q

what must happen to the electron to move up to the higher energy level?

A

it must gain energy
(by absorbing light)

THE ELECTRON IS PROMOTED TO A HIGHER ENERGY LEVEL

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73
Q

how does an electron gain energy to move up to a higher energy level?

A

by absorbing light

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74
Q

what do you say when talking about when an electron moves up to a higher energy level by absorbing light energy?

A

the electron is promoted to a higher energy level

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75
Q

where does an electron reside?

A

in the lowest energy level possible - the n=1 level (ground state)

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76
Q

what specifically must occur for an electron to move up to a higher energy level? (more details)

A
  • if light of the correct frequency and wavelength (and therefore energy) are shone on the atom, the electron will absorb that specific frequency and wavelength of light and become promoted to an energy level of higher energy

this is called an excited state

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77
Q

what is an excited state?

A

when an electron has absorbed the specific frequency and wavelength of light to be promoted to an energy level of higher energy

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78
Q

what happens to the electron that had been promoted to a higher energy level if the light source stops?

A
  • the electron will seek once again to reside in the lowest energy level
  • it must lose energy to do this
  • it does this by emitting out light
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79
Q

what are the three types of transitions or ‘series’ you need to know when looking at absorption and emission spectras?

A
  1. lyman transitions
  2. balmer transitions
  3. paschen transitions
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80
Q

what are lyman transitions?

A
  • they represent transitions from higher energy levels back down to n=1 level
  • often occur in the UV light region (long arrows)
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81
Q

what are balmer transitions?

A
  • they represent transitions from higher energy levels back down to n=2 level
  • they often occur in the visible light region
82
Q

what are paschen transitions?

A
  • they represent transitions from higher energy levels back down to the n=3 level
  • they often occur in the IR region (short arrows)
83
Q

the longer the arrow, the (more/less) energy is given out and the (lower/higher) the energy of the light emitted will be

A

the longer the arrow:
- the more energy is given out
- the higher the energy of the light emitted

84
Q

why are there several series of lines that converge?

A

because as there are several energy levels that the promoted electrons can fall back down to and they converge as the higher energy levels also converge

85
Q

for hydrogen, what are the first 4 colours of arrows for the balmer series?

A
  1. red
  2. green
  3. blue
  4. purple
86
Q

what is the equation for energy, using planck’s constant, energy and frequency?

A

E = hf

E = energy
h = planck’s constant, 6.63 x10^-34 Js
f = frequency, Hz or s^-1

87
Q

what is the equation for frequency, using wavelength, speed of light and frequency?

A

f = c / wavelength

f = frequency, s^-1 or Hz
y = wavelength, m
c = speed of light, m s^-1

88
Q

what is the equation linking wavelength, frequency and light?

A

E = hc / y

E = energy, J
h = planck’s constant, 6.63 x10^-34 Js
c = speed of light, m s^-1
y = wavelength, m

89
Q

what is the relationship between wavelength and energy?

A

they are inversely proportional

90
Q

what is the relationship between frequency and energy?

A

they are directly proportional

91
Q

what is the relationship between wavelength and frequency ?

A

they are inversely proportional

92
Q

in increasing energy order, what is the order of the different types of light? (x-rays, visable light, infrared, ultra violet, radio waves)

A

radio waves -> infrared-> visible light -> ultra violet -> x-rays -> gamma rays

(increasing wavelengths the opposite way)

93
Q

what happens when white light passes through a gas?

A

that gas absorbs certain frequencies of the light

( these frequencies correspond to the exact energy differences between the atom’s quantised levels)

94
Q

what does the sun emit?

A

white light

95
Q

what happens in the hydrogen absorption spectrum?

A
  1. white light is shone onto hydrogen gas
  2. the electrons in the hydrogen atoms absorb certain frequencies of light
  3. the absorbed frequencies are now black lines and are absent from the spectrum as they have been absorbed by the hydrogen atom’s electrons
96
Q

are all frequencies (and therefore colours) of light absorbed by the hydrogen atoms? why?

A

no - because the energy levels are quantised and so energy from the white light can only be absorbed if the energy it has is exactly the same as the energy difference between two energy levels

97
Q

what is the black line on the right of the absorption spectrum of hydrogen and what does it represent?

A
  • it is the lowest energy transition
  • it represents the electron being promoted from the n=2 level to the n=3 level
98
Q

what happens in the hydrogen emission spectrum?

A
  1. a current is passed through hydrogen gas. this excites electrons in the atoms
  2. the photons of light are collected as they drop down from the higher to lower energy levels. this will produce a series of coloured lines on a mainly black background - showing that light is only emitted at certain frequencies relating to certain jumps
99
Q

are all frequencies (and therefore colours) of light emitted by the hydrogen atoms? why?

A

no - because the energy levels are quantised and so energy from the electrons jumping down from higher to lower energy levels is emitted, have certain discrete energies and therefore colours on an emission spectrum

100
Q

what are the only transitions we can see in the visible region when looking at hydrogen’s emission spectrum?

A
  • visible transitions (= Balmer transitions)

(this does not mean there are not any other transition such as Lyman and Paschen - as these transitions occur in the IR and UV part of the spectrum which we cannot see with the naked eye)

101
Q

because the only transitions we can see are the Balmer transitions when looking at hydrogen’s emission spectra, does this mean there aren’t any other transitions?

A

no - this does not mean there are not any other transition such as Lyman and Paschen - as these transitions occur in the IR and UV part of the spectrum which we cannot see with the naked eye)

102
Q

what is the red line on the right of the hydrogen emission spectrum and what does it represent?

A
  • it is the lowest energy transition
  • it represents the electron jumping from the n=3 to the n=2 level
103
Q

if you have kJ but want to find kJ mol^-1, what must you do?

A

x by avogadro’s number

___ x avogadro’s number =___mol^-1

104
Q

when a question asks for an appropriate number of significant figures, what do you put it to?

A

whatever they’ve given their numbers in

(if multiple numbers e.g 4500 and 2364, give it to whatever is the lowest number of significant figures given e.g 2 sig figs)

105
Q

why are electrons able to take ip multiple different energies?

A

cause they have multiple different energy levels to move up to

106
Q

when does ionisation occur?

A

when an electron gets promoted past the convergence limit

107
Q

what is below the n=1 level?
what is above the n=infinite level?

A
  • below the n=1 level is the nucleus
  • above the n=infinite level is the outside of the atom
108
Q

how are you able to work out the ionisation energy of the hydrogen atoms?

A
  • if we know the frequency of wavelength of the convergence limit of the lyman series

(measuring the convergent frequency of the lyman series (difference from
n=1 to n=infinite) and usign ∆E=hf allows the ionisation energy to be calculatred. the value of ∆E is multiplied by avogadros constant to give the first ionisation energy for a mole of atoms)

109
Q

what element is used when looking at absorption and emission spectras at AS level?

A

hydrogen

110
Q

would the order of red, green, blue then purple of the arrows for the Balmer transition of hydrogen be the same for every element?

A

no - it would change per element

111
Q

how is a beta particle formed?

A

when a neutron breaks down to form a proton and an electron

(the proton stays in the nucleus, the electron is emitted as a beta particle)

112
Q

what does a change in atomic number mean?

A

a different element

113
Q

what is the mnemonic to remember the order that the shells/orbitals fill up?

A

stupid people die first
s, p, d, f

114
Q

what is the nature of the radiation of alpha?

A
  • it is a helium nucleus if 2 protons and 2 neutrons
  • has a mass of 4
  • has a charge of +2
115
Q

what is the nature of the radiation of beta?

A
  • high kinetic energy electrons
  • mass roughly 1/2000
  • charge -1
116
Q

what is the nature of the radiation of gamma?

A
  • high frequency electromagnetic radiation
  • mass of 0
  • charge of 0
117
Q

what is the penetrating power of alpha?

A
  • low
  • bc biggest mass and charge, stopped by a few cm of air or thin sheet of paper
118
Q

what is the penetrating power of beta?

A
  • medium
  • stopped by aluminium
119
Q

what is the penetrating power of gamma?

A
  • very high
  • bc smallest mass, most is stopped by a thick layer of steel or concrete but even a few cm of dense lead doesn’t stop all of it
120
Q

what is the ionising power of alpha?

A
  • very high
  • bc the biggest mass and charge, has the biggest ‘punch’
121
Q

what is the ionising power of beta?

A
  • moderate ionising power
  • bc smaller mass and charge than the alpha particle
122
Q

what is the ionising power of gamma?

A
  • low
  • bc carries no electric charge and has virtually no mass, so not much of a ‘punch’ when colliding with an atom
123
Q

what is the max number of electrons a s orbital can have?

A

2

124
Q

what is the max number of electrons a p orbital can have?

A

6 electrons

125
Q

what is the max number of electrons a d orbital can have?

A

10 electrons

126
Q

why do you draw one arrow up and one arrow down in electronic configuration?

A

a maximum if 2 electrons can occupy any orbital, each with opposite spin

127
Q

what do the chemical properties of an atom depend on?

A

the electronic configuration

(so isotopes have the same chemical properties as they have the same electronic configuration)

128
Q

what has no affect on the chemical properties of an atom? why?

A

the neutron number

(they have no charge and hence exert no attractive force on the nucleus)

129
Q

therefore, why do isotopes tend to have very similar chemical properties?

A

since they have the same atomic number and the same electronic configuration

(they differ only in number of neutrons, which do not directly influence the chemical properties of an element)

130
Q

what effect does alpha decay have on the mass number and the atomic number?

A

mass number -4
atomic number -2

131
Q

what effect does beta decay have on the mass number and the atomic number?

A

mass number = 0
atomic number +1

132
Q

what is ionisation energy?

A

the energy required to remove an electron and produce an ion

133
Q

explain the trend in ionisation energy across a period

A

ionisation energy generally increases as you move left to right across a period

134
Q

explain the trend in ionisation energy down a group

A

ionisation energy decreases down a group

135
Q

why does the amount of energy needed to remove electrons increase?

A

as you remove each electron, you are creating an ion. the attraction is now stronger

136
Q

first ionisation energy definition

A

the energy required to remove the outer electron of a gaseous atom to form a +1 ion

e.g Na(g) —> Na + (g) + e -

137
Q

what are the three factors that affect ionisation energy?

A
  • nuclear charge (no. of protons)
  • atomic radius (size of atom)
  • the number of electrons between the outer electron and the nucleus (shielding)
138
Q

how does the nuclear charge affect ionisation energy?

A
  • the more protons in the nucleus, the more positively charged the nucleus is, and the more strongly the outer electron is attracted to it
    (going across a period)
139
Q

how does the atomic radius affect ionisation energy?

A
  • attraction falls off very rapidly with distance
  • an electron close to the nucleus will he much more strongly attracted than one further away

(going down the group)

140
Q

how does the number of electrons between the outer electrons and the nucleus affect ionisation energy?

A
  • the outer shell electrons are repelled by any inner shells between the electrons and the nucleus
  • this repelling effect, called electron shielding or screening, reduces the overall attractive force experienced by the outer shells
  • the more filled inner shells or subshells there are, the smaller the attractive force on the outer electron
141
Q

what elements have the highest ionisation energies?
(cause the peaks on the graph)

A

noble gases

142
Q

what elements have the lowest ionisation energies?
(cause the troughs on the graph)

A

alkali metals

143
Q

do the ionisation energy in the troughs and peaks slowly increase or decrease?

A

decrease

144
Q

what are some example of the blips in the ionisation energies?

A
  • boron is lower than beryllium
  • oxygen is lower than nitrogen
145
Q

why does boron have a lower ionisation energy than beryllium?

A

it’s easier to remove the outer electron as it’s further away from the nucleus so it’s less attracted to the nucleus

(show sub-shells)

146
Q

why does oxygen have a lower ionisation energy than nitrogen?

A

it’s easier to remove electron due to repulsion

(a half filled shell is more stable)

147
Q

what isotope is used in radiotherapy for the treatment of cancer?

A

cobalt-60

(the high energy of gamma radiation is used to kill cancer cells)

148
Q

what isotope is normally used as a medical tracer?

A

technetium-99m

149
Q

what isotope is used in carbon dating?

A

carbon-14

150
Q

what isotope is used in estimating the geological age of rocks?

A

potassium-40

it can change into argon-40 by the nucleus gaining an inner electron. measuring the ratio of potassium-40 to argon-40 in a rock gives an estimate of its age

151
Q

ionisation definition

A

the process of removing electrons from an atom

152
Q

what is the shielding effect/screening?

A

the repulsion between electrons in different shells. inner shell electrons repel outer shell electrons

153
Q

how many ionisation energies does an element have?

A

as many as it has electrons

e.g the third ionisation energy:
Na 2+ (g) —> Na 3+ (g) + e -

154
Q

why does the ionisation energy increase as you remove electrons from an atom?

A
  • there is a greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons
  • as each electron is removed there is less electron-electron repulsion and each shell will be drawn in slightly closer to the nucleus
  • as the distance of each electron from the nucleus decreases, the nuclear attraction increases
155
Q

when does radioactive emission occur?

A

when an unstable nucleus becomes more stable by giving out energy and, in most cases, small particles such as electrons

156
Q

other than gamma radiation, when else is gamma radiation emitted?

A

after a process called electron capture

electron capture occurs when a proton-rich nucleus absorbs an inner electron. this electron combines with a proton to form a neutron

157
Q

does gamma radiation have high or low energy?
high or low frequency?
long or short wavelength?

A

high energy
high frequency
short wavelength

158
Q

how does gamma radiation ionise atoms?

A

only if the electrons absorb the energy of the gamma radiation
however this is unlikely given that gamma radiation has such a short wavelength

159
Q

why are positrons more strongly attracted to the negative plate than alpha particles?

A

because they have a lower mass

160
Q

when using a tracer, what is important to make sure?

A
  • it has a short half life, so that it decays quickly before it can do any permanent damage
  • it emits enough radiation to be detected outside of the body
161
Q

what is the evidence for electrons existing in shells?

A

the study of ionisation energies provide very clear evidence for shells of electrons

162
Q

why is there a general increase in ionisation energy from lithium to neon?

A

due to the increased nuclear attraction l, since distance to the nucleus is constant, shielding is constant and the number of protons is steadily increasing

163
Q

why does the excited state need to lose energy?

A

its unstable

164
Q

what are photons?

A
  • light can be considered as energy packets called photons
  • they have both the properties of a ‘particle’ or a transverse wave
165
Q

what is the name for when outer electrons feel less of the positive attraction of the nucleus due to inner electrons?

A

shielding

166
Q

what is the type of decay that occurs when a neutron breaks down into a proton and a high energy electron?

A

beta

167
Q

what is energy directly proportional to?

A

frequency

168
Q

what is the name for when the energy levels of an atom get closer together?

A

convergence

169
Q

the greater the frequency, the ___ the energy?
the greater the wavelength, the ___ the frequency?

A

the greater the frequency, the higher thr energy
the greater the wavelength, the lower the frequency

170
Q

how are the Lyman series and ionisation energy linked?

A

transition from n=infinite to n=1 can be used to calculate IE using E = hv

171
Q

the greater the nuclear charge, the ___ the ionisation energy?

A

greater the nuclear charge, the greater the ionisation energy

172
Q

the greater the atomic radius, the ___ the ionisation energy?

A

the greater the atomic radius, the lower the ionisation energy

173
Q

the greater the shielding, the ___ the ionisation energy?

A

the greater the shielding, the lower the ionisation energy

174
Q

relative atomic mass definition

A

the weighed average mass of all isotopes compared to 1/12th the mass of C12

175
Q

explain why neon has a lower first ionisation energy than helium?

A

although Ne has a higher nuclear charge, it also has greater shielding and atomic radius which outweighs this

176
Q

what happens when a positron comes into contact with an electron?

A

they annihilate each other and create gamma radiation

177
Q

are radioisotopes with a longer or shorter half-life more dangerous?

A

short half lives, because it decays very quickly and thus emits a large dose of radiation over a short period of time, causing more damage to living cells

(but radioisotopes with a long half life are more of an environmental problem as it takes a long time to decrease to a safe level)

178
Q

what shape are s-orbitals?

A

spherical

179
Q

what shape are p orbitals?

A

dumb-bell shaped

180
Q

what is the name of how energy levels are split into regions of space around the nucleus where there is a high probability of finding an electron of a particular energy?

A

orbitals

181
Q

what are atomic orbitals?

A

regions in space where electrons may be found

182
Q

what are energy levels split into?

A

sub-levels (subshells) which contain orbitals of the same type

183
Q

how many electrons can each orbital contain?

A

a maximum of 2 electrons

184
Q

as there are 3 p orbitals, with each one holding __ electrons, p subshell can hold __ electrons

A

2
6

185
Q

suggest why compounds containing B3+ ions are unlikely to exist?

A

too much energy is required to form B3+ ions

186
Q

when do cations (positive ions) form?

A

when an atom loses one or more electrons

187
Q

when do anions (negative ions) form?

A

when an atom gains one or more electrons

188
Q

why is radiation bad for living cells?

A

high energy radioactive emissions break chemical bonds in the cell molecules giving rise to changes in DNA which can cause mutations and thr formation of cancerous cells at lower doses, or cell death at higher doses

189
Q

how can you monitor the thickness of metal strops or foil?

A
  • the metal is placed between two rollers to get the right thickness
  • a radioactive source ( a beta emitter) is mounted on one side of the metal with a detector on the other.
  • if the amount of radiation reaching the detector increases, the detector operates a mechanism for moving the rollers apart and vice versa
190
Q

how are electrons held in their shells?

A

by their attraction to the positive nucleus

191
Q

why will successive ionisation energies always increase?

A
  • there is a greater effective nuclear charge as the same number of protons are holding fewer and fewer electrons
  • as each electron is removed there is less electron-electron repulsion and each shell will be drawn in slightly closer to the nucleus
  • as the distance of each electron from thr nucleus decreases, the nuclear attraction increases
  • but a larger increase shows that an electron has been removed from a new shell
192
Q

molar first ionisation energy definition

A

the energy required to remove one mole of electrons from one mole of gaseous atoms

193
Q

explain why the lines become closer together at the high frequency end of the spectrum?

A

the (electron) energy levels of a hydrogen atom become closer

194
Q

electron deficient definition

A

when the outer shell of electrons is not full

195
Q

e.g Aluminium
why does it have a big jump in ionisation energy between it’s 3rd and 4th?

A
  • it has 3 electrons in its outer shell
  • so largest jump between 3rd and 4th IE
196
Q

explain how the lyman series can be used to calculatr the ionisation energy of hydrogen?

A
  • measuring the wavelength at the convergence limit
  • calcuate the ionisation enrrgy using E=hf
197
Q

what units is wavelength usually in f=c/wavelength

A

wavelength = meters

198
Q

david said that sodium compounds give a yellow flame test because the heat makes the atoms move faster. he also said that the yellow flame was the sodium absorption spectrum consisting of one line because the atoms take in light of just one energy.

discuss how far you agree with david’s statement and correct any errors whcih he has made.

A
  • not an absorption spectrum/ is an emission spectrum
  • (it is not atoms) but electrons that are excited
  • (electrons) go to higher energy levels
  • then they fall back (to lower energy levels)
  • they emit energy
  • sodium spectrum has more than 1 line
  • the flame colour is yellow because the energy emitted is in the yellow part of the visible spectrum
  • series of lines that come closer together (wirh increase in energy involved)
199
Q

state the relationship between energy, frequency and wavelength [2] (equations)

A

E = hf (1)
c = f λ (1)

200
Q

as successive electrons are removed, the value of the ionisation energy increases due to a _____________?

A

greater effective nuclear charge

201
Q

atomic orbital definition

A

a region in an atom that can hold up to two electrons with opposite spins

as level chemistry (16 decks)

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