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AQA A Level Physical Chemistry > 1. Atomic Structure > Flashcards

1. Atomic Structure Flashcards

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1
Q

What happened in 1662 to support the development of the atom?

A

Robert Boyle proposed that some substances could not be made simpler

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2
Q

What happened in 1803 to support the development of the atom?

A

John Dalton suggested elements were composed of atoms that could not be broken down

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3
Q

What happened in 1896 to support the development of the atom?

A

Henri Becquerel discovered radioactivity - showing particles could come from inside the atom

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4
Q

What happened in 1911 to support the development of the atom?

A

Ernest Rutherford found that most of the mass and charge of the atom is concentrated in a tiny central nucleus

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5
Q

What is the relative mass of an electron?

A

1/1840

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6
Q

What are protons and neutrons held in the centre of atoms by?

A

The strong nuclear force

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7
Q

What does the strong nuclear force, holding together the protons and neutrons, overcome?

A

Electrostatic forces of attraction that hold electrons and protons together in the atom

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8
Q

What letter is sometimes used to represent the mass number?

A

A

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9
Q

What letter is sometimes used to represent the atomic number?

A

Z

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10
Q

What is the mass number?

A

The total number of neutrons and protons in the nucleus

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11
Q

What is the atomic number?

A

The number of protons in the nucleus

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12
Q

What is the atomic number also called?

A

The proton number

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13
Q

What determines the chemical properties of an element?

A

The number of electrons in the outer shell

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14
Q

How many electrons does the first shell hold?

A

2

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15
Q

How many electrons does the second shell hold?

A

8

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16
Q

How many electrons does the third shell hold?

A

18

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17
Q

How many electrons does the fourth shell hold?

A

32

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18
Q

What expression shows the number of electrons in each shell? (where n is the number of the shell)

A

2n²

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19
Q

What will change for isotopes of the same element, in terms of chemical and physical properties?

A

Chemical properties will stay the same with each isotope, but physical properties will change due to the change in mass

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20
Q

How can relative atomic mass be worked out?

A

Average mass of one atom ÷ 1/12 mass of 1 atom of C-12

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21
Q

How can relative molecular mass be worked out?

A

Average mass of one molecule ÷ 1/12 mass of one atom of C-12

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22
Q

What is Mr?

A

Relative molecular mass

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23
Q

What is Ar?

A

Relative atomic mass

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24
Q

What does the mass spectrometer do?

A

Determines the relative isotopic mass and relative abundance for each isotope

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25
Q

An overview of how a time of flight mass spectrometer works?

A

The substances in the sample are converted to positive ions, accelerated and then arrive at a detector

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26
Q

What is relative isotopic mass?

A

Mass of each individual isotope relative to carbon-12

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27
Q

What an important initial condition required when using a time of flight spectrometer?

A

The apparatus is kept under high vacuum

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28
Q

Why is the time of flight apparatus kept under a high vacuum?

A

To prevent the ions that are produced from colliding with molecules from the air

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29
Q

What must happen if the sample isn’t a gas before entered into a mass spectrometer?

A

It must be vaporised

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30
Q

What are the two ways that a sample can be ionised in preparation for mass spectrometry?

A
  • electron impact

* electrospray ionisation

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31
Q

What happens in electron impact?

A
  • gaseous sample entered into mass spectrometer
  • bombarded with high speed electrons from an electron gun
  • knocks out an electron (or two) from the atom/molecule
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32
Q

What is the electron gun formed from for electron impact?

A

A hot wire filament with a current running through it that emits electrons

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33
Q

How many electrons are knocked out of the atom in electron impact?

A

Usually one, but sometimes two

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34
Q

Why is only one electron usually knocked out of an atom during electron impact?

A

It requires a lower energy than two, so is more likely

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35
Q

When is electron impact used?

A

For elements and substances with a low formula mass

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36
Q

When molecules are ionised using electron impact, what are the 1+ ions formed known as?

A

Molecular ions

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37
Q

Can molecules be ionised?

A

Yes

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38
Q

Equation for ionisation of methane using electron impact?

A

CH4 -> CH4+ + e-

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39
Q

Which method of ionisation for mass spectrometry often breaks down the molecular ion into smaller fragments?

A

Electron impact

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40
Q

What charge is required on ions during mass spectrometry?

A

Positive

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41
Q

What happens in electrospray ionisation?

A
  • sample dissolved in solvent
  • sample injected through fine needle to give fine mist
  • tip of needle attached to +ve side of power supply
  • particles gain a proton
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42
Q

In which method of ionisation for mass spectrometry do atoms gain a proton?

A

Electrospray ionisation

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43
Q

What is the technical name for the fine needle in electrospray ionisation?

A

Hypodermic

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44
Q

What is the mass of new ions in electrospray ionisation?

A

Mr + 1

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45
Q

Equation for ionisation using electrospray ionisation?

A

X + H+ -> XH+

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46
Q

What eventually happens to the solvent that was added in electrospray ionisation?

A

It is evaporated

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47
Q

What charge does the needle have in electrospray ionisation?

A

Postive

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48
Q

What kind of substance is electron impact used for?

A

Substances with low formula mass

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49
Q

What kind of substance is electrospray ionisation used for?

A

Substances with higher molecular mass (e.g. proteins)

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50
Q

In which type of ionisation does fragmentation rarely occur?

A

Electrospray ionisation

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51
Q

Where do substances gain a proton from in electrospray ionisation?

A

From the solvent

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52
Q

What happens after substances are ionised in mass spectrometry?

A

They are accelerated

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53
Q

How are the ions accelerated in mass spectrometry?

A

Using a negatively charged plate

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54
Q

Why are ions accelerated during mass spectrometry?

A

So that they all have the same kinetic energy

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55
Q

Which particles will have a higher velocity during mass spectrometry?

A

Lighter particles

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56
Q

What is the equation for the velocity of each particle during acceleration?

A

v = √2KE ÷ m

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57
Q

What does the velocity of each particle depend on in mass spectrometry? Why is this?

A

It depends on the mass as the kinetic energy is the same for all particles

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58
Q

What happens after ions are accelerated during mass spectrometry?

A

They pass through a hole in the negatively charged plate, forming a beam

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59
Q

When do ions move through the flight tube during mass spectrometry?

A

After they have passed through the hole in the negatively charged plate

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60
Q

What does the time of flight of a particle depend on?

A

Its velocity; which in turn depends on its mass (and charge)

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61
Q

What expression is used to give time of flight?

A

t = d/v

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62
Q

How is the equation for velocity incorporated into the expression for time of flight?

A

t = d/ √2KE ÷ m

63
Q

What is time of flight proportional to?

A

The square root of the mass

64
Q

What happens when the ions reach the detector in mass spectrometry?

A

They gain an electron from the detector, generating a movement of electrons and therefore an electric current

65
Q

What does the size of the current in the detector show during mass spectrometry?

A

The size of current gives a measure of the number of ions hitting the plate

66
Q

What happens to the signal from the detector during mass spectrometry?

A

It is passed to a computer which generates a mass spectrum

67
Q

What does a mass spectrum show?

A

The mass to charge (m/z) ratio and abundance of each ion

68
Q

Why is m/z effectively the mass of each ion?

A

All ions produced by electrospray ionisation and most by electron impact have a 1+ charge

69
Q

Can ions formed by electrospray be 2+?

A

No

70
Q

Which signal is from the molecular ion on a mass spectrum?

A

The peak furthest to the right (greatest m/z value)

71
Q

For molecules ionised by electrospray, what is the relative molecular mass?

A

The signal with the greatest m/z value minus 1

72
Q

Why are the relative molecular masses of molecules ionised by electrospray the greatest m/z value minus 1?

A

Due to the gaining of a proton during ionisation and then gaining an electron during detection

73
Q

Why are different isotopes detected separately during mass spectrometry?

A

They have different masses

74
Q

How many decimal places can mass spectrometers measure to?

A

5 - however most is done to 1 d.p.

75
Q

What is low resolution mass spectrometry?

A

When relative atomic masses are only worked out to 1 d.p.

76
Q

What is the definition of relative atomic mass?

A

The average mass of one atom of an element compared to 1/12 of the mass of one atom of carbon-12

77
Q

How is Ar calculated?

A

(mass no. x abundance)+(mass no. x abundance) / total abundance

78
Q

What happens in a mass spectrum if the ion has a 2+ charge?

A

The m/z value will be half the mass

79
Q

What happens to the mass spectrum if the sample is a molecule?

A

The molecule can either split up or remain as a molecular ion

(molecular ions easily identified as it’s the last large peak along m/z axis)

80
Q

What happens if a molecule does not split up during mass spectrometry in terms of its isotopes?

A

Each atom can have various combinations of isotopes (e.g. Cl-35 - Cl37+

81
Q

Uses of mass spectrometers?

A
  • investigate illegal drugs, explosives and chemical pills

* space probes - to identify elements in rock sample or gases in the atmosphere

82
Q

How many decimal places are relative atomic masses usually to?

A

1

83
Q

How are electrons arranged around the nucleus?

A

In energy levels

84
Q

What are shells also called?

A

Main energy levels

85
Q

How are main energy levels labelled?

A

1, 2, 3 etc.

86
Q

What formula is used to give the maximum number of electrons in a main energy level?

A

2n²

87
Q

Which main energy level cannot be divided into sub levels?

A

The first (s only)

88
Q

What are main energy levels divided into?

A

Sub-levels

89
Q

How are sub-levels labelled?

A

s, p, d, f

90
Q

What happens to energy of electrons as distance from the nucleus increases?

A

It increases

91
Q

What does each sub-level consist of?

A

Orbitals

92
Q

How many electrons can orbitals hold?

A

2

93
Q

How many orbitals are in the s sub-level?

A

1

94
Q

How many orbitals are in the p sub-level?

A

3

95
Q

How many orbitals are in the d sub-level?

A

5

96
Q

How many orbitals are in the f sub-level?

A

7

97
Q

How is the arrangement of electrons for any atom given?

A

using:

  • main energy level
  • sub-level
  • number of electrons in each sub-level
98
Q

After 1s, 2s, 2p, 3s, and 3p, what happens?

A

The next electon goes into 4s, skipping 3d

99
Q

Why is 4s before 3d?

A

The 3d sub-level has a higher energy

100
Q

How is the electron considered now (instead of a particle)?

A

As a cloud of negative charge

101
Q

What is the volume of space that an electron fills up called?

A

Its atomic orbital

102
Q

What does the first main energy level consist of?

A

A single s-orbital

103
Q

What does the second main energy level consist of?

A

A single s-orbital and 3 p-orbitals

104
Q

How many electrons can s sub-levels hold?

A

2

105
Q

How many electrons can p sub-levels hold?

A

6

106
Q

How many electrons can d sub-levels hold?

A

10

107
Q

How many electrons can f sub-levels hold?

A

14

108
Q

What order are sub-levels filled in?

A

1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s, 4d, 5p, 4f, 5d

109
Q

Where is the f block on the periodic table?

A

The (separate) bottom two rows

110
Q

Where is the s block on the periodic table?

A

First two columns

111
Q

Where is the d block on the periodic table?

A

Where the transition metals are

112
Q

Where is the p block on the periodic table?

A

The right hand side

113
Q

What does chlorine being in the p-block tell us?

A

The highest energy sub-shell is a p subshell

114
Q

What does chlorine being in period 3 tell us?

A

The highest energy sub-shell will be the 3 sub-shell

115
Q

What happens when writing the electronic configuration of ions?

A

Electrons are added or subtracted from the total

116
Q

What happens when working out the ion configuration for transition metals?

A

Electrons are firstly removed from 4s and then from 3d

117
Q

What spins do electrons in the same orbit have?

A

Opposite

118
Q

Why do electrons in the same orbit have opposite spins?

A

Like charges will repel

119
Q

How are the electrons represented in spin diagrams?

A

Arrows pointing up or down to show the different directions of spin

120
Q

What are the three rules for allocating electrons to atomic orbitals?

A
  1. orbitals of lower energy are filled first
  2. orbitals of the same energy fill singly before pairing starts
  3. no orbital can hold <2 electrons
121
Q

Why do orbitals fill singly before pairing starts?

A

The electrons repel each other

122
Q

Why are some sub-levels half filled?

A

A half sub-level is quite stable

123
Q

What is ionisation energy?

A

The energy required to remove a mole of electrons from a mole of atoms in the gaseous state

124
Q

What is the first ionisation energy?

A

The energy required to remove one electron from a gaseous atom

125
Q

What state must a substance be before it is ionised?

A

A gas

126
Q

What is ionisation energy measured in?

A

kJ mol-1

127
Q

Why does the first electron need the least energy to remove?

A

It is being removed from a neutral atom

128
Q

What are successive ionisation energies?

A

The energy to required to remove further electrons one by one

129
Q

What charge is the particle when 2nd, 3rd, 4th etc. ionisation energies are measured?

A

Positive

1+ for 2nd, 2+ for 3rd etc.

130
Q

What is effective nuclear charge?

A

Attraction between the nucleus and outer electrons when shielding is taken into account

131
Q

Which factors can affect ionisation energy?

A
  • distance between outer electrons and nucleus
  • how many electron shells there are - ‘shielding’
  • nuclear charge - proton no.
132
Q

How does shielding affect ionisation energy?

A
  • More electron shells = more -ve charges to repel electrons

* So more shells means it’s easier to lose electrons

133
Q

What is the general trend in first ionisation energies across period 3?

A

They increase

134
Q

Does shielding affect first ionisation energy across period 3?

A

No, as there is the same number of shells

135
Q

Why does first ionisation energy generally increase across period 3?

A

• proton number ↑ so nuclear charge ↑ (so ↑ charge

136
Q

Why does the atomic radius decrease slightly across period 3?

A

Due to increase in positive charge on the nucleus

137
Q

What are the exceptions to the trend in IE of period 3 elements?

A

Two drops in the graph - from Mg to Al and from P to S

138
Q

Why is there a drop in the period 3 IE graph from Mg to Al?

A
  • Mg electron removed from s sub-level whereas Al moved from P
  • P higher in energy
  • so Al is easier to remove
139
Q

Why is there a drop in the period 3 IE graph from P to S?

A
  • Both are removed from the p sub-level
  • But S has a pair of electrons in the p orbital which repel
  • This makes the electron from S easier to remove`
140
Q

What is mutual repulsion?

A

When electrons in the same orbital repel each other

141
Q

What is the general trend in first ionisation energies down group 2?

A

It decreases

142
Q

Why does first ionisation energy decrease down group 2?

A
  • increase in shells
  • so increase in distance from nucleus
  • so shielding increases
143
Q

Why are outer electrons lost first during ion formation?

A

They are the easiest to remove

144
Q

Why does ionisation energy down a group decrease, even though nuclear charge increases?

A

Increased shielding and distance outweigh this

145
Q

Why do successive ionisation energies increase?

A
  • same number of protons but fewer electrons
  • so electrons are more strongly attracted to the nucleus
  • and harder to remove
146
Q

What does a large increase in successive ionisation energies suggest?

A

That the electron is being removed from an electron shell closer to the nucleus

147
Q

Where does the peak furthest to the right on a mass spectrometer come from?

A

The molecular ion - and it’s m/z value gives the relative atomic mass

148
Q

Aluminium’s first 3 electrons come from energy level 3, whereas the 4th is removed from energy level 2. What effect will this have on the 4th IE compared to the other 3?

A

4th IE will be much greater as it’s being removed from an energy level closer to the nucleus, so stronger nuclear attraction

149
Q

Why does the first ionisation energy of atoms generally increase across a period?

A

Proton number increases so nuclear attraction increases

150
Q

Why is the first ionisation energy of boron less than that of beryllium?

A

Boron’s outer electron is removed from the p sub-level which is further from the nucleus so easier to remove

151
Q

Why do first ionisation energies decrease down a group?

A

Greater distance from nucleus, and more shielding, means there’s less nuclear attraction

152
Q

Why is the second ionisation energy of sodium much greater than the first?

A

2nd electron removed from a more positive species so electrons are being attracted more - greater nuclear attraction

153
Q

Examples of solvents used in electrospray ionisation?

A
  • water

* methanol

AQA A Level Physical Chemistry (12 decks)

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