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Chem A-level > 3.1.1 Atomic Structure PPQs > Flashcards

3.1.1 Atomic Structure PPQs Flashcards

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1
Q

Explain how gaseous atoms of Rubidium are ionised using electron impact ionisation in a mass spectrometer. [2 marks]

A
  • high energy electrons fired at sample from an electron gun
  • high energy electrons knock off one electron from each atom, forming a positive ion
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2
Q

Write an equation, including state symbols, to show the process that occurs when the first ionisation energy of rubidium is measured using electron impact ionization. [1 marks]

A

Rb(g) → Rb+(g) + e–

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3
Q

State one reason why the first ionisation energy of rubidium is lower than the first ionisation energy of sodium. [1 mark]

A
  • Rb is a bigger atom so electron further from nucleus
  • electron lost from a higher energy level
  • more shells so More shielding in Rb so less attraction of nucleus in Rb for outer electron
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4
Q

By reference to the relevant part of the mass spectrometer, explain how the
abundance of an isotope in a sample of rubidium is determined. [2 makrs]

A

Relevant part: Detector
Explanation: Current / electrical signal produced proportional to abundance

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5
Q

Predict whether an atom of 88Sr will have an atomic radius that is larger than,
smaller than or the same as the atomic radius of 87Rb. Explain your answer. [3 marks]

A
  • Smaller
  • Bigger nuclear charge / more protons in Sr
  • Same shielding
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6
Q

Predict the element in Period 3 that has the highest 2nd IE [2 markks]

A

Na - electron removed from the 2p orbital

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7
Q

Explain why the IE of every element is endothermic [1 mark]

A

energy needed to overcome the attraction between the negative electron and positive nucleus

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8
Q

define the term relative atomic mass [2 marks]

A

average mass of one atom of an element / 1/12 mass of one atom of 12C

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9
Q

which isotope is deflected most by magnetic field of a mass spectrometer?

A

the one with lowest m/z

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10
Q

complete the electronic configuration of tellurium: [Kr]

A

[Kr] 5s2 4d10 5p4

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11
Q

suggest what might cause the relative atomic mass of an element from a mass spec to be different to the one on the periodic table

A
  • other isotopes present/some isotopes absent
  • different abundances of isotopes
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12
Q

predict whether the atomic radius of 124Te is larger than, smaller than, or the same as, the atomic radius of 130Te [2 marks]

A

the same
same no. protons AND same electron configuration

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13
Q

Identify the period 3 element that has the highest melting point. Explain your answer. [4 marks]

A
  • silicon
  • macromolecular structure
  • covalent bonds between atoms
  • many strong covalent bonds need lots of energy to break
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14
Q

which transition metals have exactly 3 unpaired electrons in their ground state?

A

Vanadium and Cobalt

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15
Q

Name the two methods of ionisation in a mass spectrometer

A

electrospray and electron impact ionisation

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16
Q

which transition metal has only 1 unpaired d electron as an atom?

A

Scandium

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17
Q

An atom has 2 more protons and 3 more neutrons than an atom of 52Cr.
Deduce the symbol, including the mass number and the atomic number, for this atom.

A

57 26 Fe

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18
Q

State two differences between the ‘plum pudding’ model and the model of atomic structure used today.

A
  • central nucleus contains protons and neutrons
  • Electrons are now arranged in energy levels/shells/orbitals
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19
Q

Magnesium exists as three isotopes: 24Mg, 25Mg and 26Mg. In terms of sub-atomic particles, state the difference between the three isotopes of magnesium. State how, if at all, the chemical properties of these isotopes differ and give a reason for your answer. [3 marks]

A
  • 24Mg has 12n; 25Mg has 13n; 26Mg has 14n OR They have different numbers of neutrons
  • No difference in chemical properties Because all have the same electronic structure (configuration)
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20
Q

Table 1 shows some data about fundamental particles in an atom. An atom of hydrogen can be represented as 1H. Use data from Table 1 to calculate the mass of this hydrogen atom.

A

1.6734 × 10^−24 g

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21
Q

Which one of the following is a fundamental particle that would not be deflected by an electric field?

A electron

B neutron

C proton

A

B neutron

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22
Q

Deduce the number of protons in 182W

A

74

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23
Q

Deduce the number of neutrons in 186W

A

112

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24
Q

Define the term atomic number.

A

Number of protons in the nucleus

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25
Q

Explain why atoms of an element may have different mass numbers.

A

They may have different numbers of neutrons

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26
Q

When He2+ particles were fired at a thin sheet of gold, most of the particles were detected at point P. What conclusion can be drawn from the detection of He2+ particles at point P?

A

Gold atoms are mainly empty space.

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27
Q

When He2+ particles were fired at a thin sheet of gold, about 1 in 8000 of the particles were detected at point Q. What conclusion can be drawn from the detection of He2+ particles at point Q?

A

Gold atoms have a small, positive nucleus

28
Q

Define the term relative atomic mass.

A

average mass of an atom or isotopes divided by the mass of 1 atom of 12C, multiplied by 12

29
Q

Explain, in detail, how the relative atomic mass of an element can be calculated from data obtained from the mass spectrum of the element.

A
  • Spectrum gives (relative) abundance and m/z
  • Multiply m/z by relative abundance for each isotope
  • Sum these values
  • Divide by the sum of the relative abundances
30
Q

Define the term mass number of an atom.

A

Mass number = number of protons + neutrons

31
Q

write an equation to represent the second ionisation of strontium

A

Sr+(g) -> Sr2+ + e-

32
Q

define the term ‘first ionisation energy’

A

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

33
Q

write an equation for the second ionisation energy of oxygen

A

O+(g) -> O2+(g) + e-

34
Q

On 2 axes, add crosses to estimate the successive ionisation energies of oxygen.

A
35
Q

Explain why the second ionisation energy of boron is higher than the first ionisation energy of boron.

A

Outer electron is being removed from a positive ion and therefore requires more energy

36
Q

Identify the diagram in the figure below that shows the correct relative sizes of the ions in sodium fluoride. Justify your answer.

A

B: Both Na+ and F– same electron arrangement (isoelectronic). Na+ has more protons so stronger attractions for outer electrons

37
Q

Explain why the second ionisation energy of calcium is lower than the second ionisation energy of potassium. [2 marks]

A
  • In Ca+ outer electron is further from nucleus
  • More shielding in Ca+
38
Q

Identify the s-block metal that has the highest first ionisation energy.

A

Be

39
Q

Deduce which of Na+ and Mg2+ is the smaller ion. Explain your answer.

A

Mg2+ because Mg2+ has more protons and has the same shielding

40
Q

State and explain the general trend in the values of the first ionisation energies of the elements Na to Ar. [3 marks]

A
  • Trend : Increases (1)
  • Increased nuclear charge or proton number AND the shielding remains the same (1)
  • Stronger attraction between nucleus and outer e– (1)
41
Q

Explain why the value of the first ionisation energy of magnesium is higher than that of sodium.

A
  • Increased nuclear charge
  • Same shielding
42
Q

Explain why the value of the first ionisation energy of neon is higher than that of sodium.

A
  • Electron removed from a shell of lower energy
  • Less shielding
43
Q

Predict whether an atom of 88Sr will have an atomic radius that is larger than, smaller than or the same as the atomic radius of 87Rb. Explain your answer. [3 marks]

A
  • Smaller
  • Bigger nuclear charge / more protons in Sr
  • Similar/same shielding
44
Q

The Ne atom and the Mg2+ ion have the same number of electrons. Give two reasons why the first ionisation energy of neon is lower than the third ionisation energy of magnesium.

A
  • Mg2+ ion smaller than Ne atom so Mg2+ e– closer to nucleus
  • Mg2+ has more protons than Ne / e– is removed from a charged Mg2+ion vs neutral Ne atom
45
Q

A student studying GCSE science is puzzled by data which indicate that a sodium atom is larger than a chlorine atom and that a sodium ion is smaller than a chloride ion. How should an A–level Chemistry student explain this apparently conflicting information. [6 marks]

A
  • A Cl atom has more protons in its nucleus than a Na atom has
  • Both have 3 shells of electrons
  • Electrons more strongly attracted by Cl nucleus so size smaller than Na
  • An electron shell is lost when a Na ion is formed from a Na atom
  • Inner electrons more strongly attracted so ion smaller than atom
  • An electron is added to the outer shell when a Cl ion is formed
  • Greater repulsion between shells so size of chloride ion greater than Cl atom
46
Q

Element Q forms a sulfate with formula QSO4. Which of these could represent the electronic configuration of an atom of Q?

A

B

47
Q

Tellurium is the element with atomic number of 52. Complete the electron configuration of tellurium.

A

1s2 2s2 2p6 3s2 3p6 4s2 3d10 4p6 5s2 4d10 5p4

48
Q

Explain why the first ionisation energy of sulfur is different from that of phosphorus.

A
  • e− paired in 3p orbital in S
  • Paired e− repel so less energy needed to remove
49
Q

Draw a cross on the diagram to show the first ionisation energy of aluminium.

A

Al between 500 – 700 (between Na and Mg)

50
Q

State which of the first, second or third ionisations of aluminium would produce an ion with the electron configuration 1s2 2s2 2p6 3s1

A

Second

51
Q

State the trend in first ionisation energies in Group 2 from beryllium to barium.

A
  • Decreases
  • Atomic radius increases
  • As group is descended there is more shielding
  • Less attraction between the nucleus and the outer electron
52
Q

What is the maximum number of electrons that can be accommodated in an s sub-level?

A

2

53
Q

What evidence from the diagram supports the fact that 2 electrons max can be in an s sub-level?

A

Two elements before the drop in energy to Al

54
Q

What evidence from the diagram supports the fact that the 3p sub-level is higher in energy than the 3s?

A

ionisation energy of Al < that for Mg

55
Q

What evidence from the diagram supports the fact that no more than three unpaired electrons can be accommodated in the 3p sub-level?

A
  • fall in energy from P to S
  • From Al to P there are 3 additional electrons
56
Q

Describe how the molecules are ionised using electrospray ionisation. [3 MARKS]

A
  • Sample is dissolved in a volatile solvent
  • Injected through hypodermic needle at high voltage
  • Each molecule/particle gains a proton/H+
57
Q

Explain how ions are detected and relative abundance is measured in a TOF mass spectrometer. [2 marks]

A
  • ion hits the detector and gains an electron
  • relative abundance is proportional to the size of the current
58
Q

Explain why it is necessary to ionise molecules when measuring their mass in a TOF mass spectrometer [2 marks]

A
  • Ions, not molecules, will interact with and be accelerated by an electric field
  • Only ions will create a current when hitting the detector
59
Q

A sample of ethanedioic acid was treated with an excess of an unknown alcohol in the presence of a strong acid catalyst. The products of the reaction were separated and analysed in a time of flight (TOF) mass spectrometer. Two peaks were observed at m / z = 104 and 118. Outline how the TOF mass spectrometer is able to separate these two species to give two peaks. [4 marks]

A
  • Positive ions are accelerated by an electric field to a constant kinetic energy
  • The positive ions with m / z of 104 have the same kinetic energy as those with m / z of 118 and move faster
  • Therefore, ions with m / z of 104 arrive at the detector first
60
Q

Calculate the mass, in kg, of one atom of 46Ti

A
61
Q

A molecule Q is ionised by electron impact in a TOF mass spectrometer. The Q+ ion has a kinetic energy of 2.09 x 10^–15 J. This ion takes 1.23 x 10^–5s to reach the detector. The length of the flight tube is 1.50 m Calculate the relative molecular mass of Q.

A

169

62
Q

A naturally occurring sample of the element boron has a relative atomic mass of 10.8. In this sample, boron exists as two isotopes, 10B and 11B. Calculate the percentage abundance of 10B in this naturally occurring sample of boron.

A

20%

63
Q

A sample of strontium has a relative atomic mass of 87.7 and consists of three isotopes, 86Sr, 87Sr and 88Sr. In this sample, the ratio of abundances of the isotopes 86Sr :87Sr is 1:1. Calculate the percentage abundance of the 88Sr isotope in this sample.

A

80%

64
Q

A TOF mass spectrum was obtained for a sample of barium that contains the isotopes 136Ba, 137Ba and 138Ba. The sample of barium was ionised by electron impact. Identify the ion with the longest time of flight.

A

138Ba+

65
Q

A sample contains two isotopes of Copper, 63B and 65B. 63B has an abundance 2.33 times greater than 65Cu. Calculate the relative atomic mass of the sample to one decimal place.

A

63.6

Chem A-level (10 decks)

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