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AQA - A level Chemistry > Atomic structure > Flashcards

Atomic structure Flashcards

1
Q

What is the relative charge and mass of protons?

A

Protons
Relative charge: 1+
Relative mass: 1

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2
Q

What is the relative charge and mass of neutrons?

A

Neutrons
Relative charge: 0
Relative mass: 1

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3
Q

What is the relative charge and mass of electrons?

A

Electrons
Relative charge: 1-
Relative mass: 1

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4
Q

What does an atom consist of?

A
  • nucleus containing positively charged protons and neutral charged neutrons
  • negatively charged electrons orbit nucleus in energy levels/shells
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5
Q

What is the maximum number of electrons that each shel can hold?

A

1st shell - 2 electrons
2nd shell - 8 electrons
3rd shell - 18 electrons
4th shell - 32 electrons

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6
Q

How many orbitals are there in each sub-shell?

A

s sub-shell: 1orbital
p sub-shell: 3 orbitals
d sub-shell: 5 orbitals
f sub-shell: 7 orbitals

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7
Q

What is the highest energy electron?

A
  • Electron furthest away from the nucleus
    ———-> highest energy electron (f)
    s, p, d, f
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8
Q

What is the electron configuration of Argon?

A

1s2 2s2 2p6 3s2 3p6

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9
Q

What is the electron configuration of Al2+?

A

1s2 2s2 2p6 3s1

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10
Q

What is the electron configuration of F-?

A

1s2 2s2 2p6

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11
Q

What are the 2 exceptions of the d-block atoms? Explain why

A

Chromium: 1s2 2s2 2p6 3s2 3p6 4s1 3p5
- more stable with a half full d sub-shell

Copper: 1s2 2s2 2p6 3s2 3p6 4s1 3d10
- more stable with a full d sub-shell

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12
Q

What are the exceptions of d-block ions? Explain why

A

Fe2+: 1s2 2s2 2p6 3s2 3p6 3d6
- Electrons lost from 4s sub-shell
- 4s – first in – first out

Cu2+:
1s2 2s2 2p6 3s2 3p6 3d9
- 4s sub-shell empties first

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13
Q

Does the 3d sub-shell or 4s sub-shell have higher energy?

A

3d sub-shell

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14
Q

What is an orbital?

A

A region around the nucleus that can hold up to 2 electrons

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15
Q

Define first ionisation energy

A

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

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16
Q

What is the equation for the 1st ionisation energy of boron?

A

B (g) —-> B+ (g) + e-

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17
Q

What is the equation for the 3rd ionisation energy of magnesium?

A

Mg2+ (g) —-> Mg3+ (g) + e-

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18
Q

What is the general trend of atomic radius across period 3? Explain why

A
  • Atomic radius decreases
  • As nuclear charge increases
  • Shielding stays the same
  • So greater attraction between outer electrons and nucleus
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19
Q

What is the general trend in ionisation energies across period 2? Explain why

A

-General increase
- Nuclear charge increases
- Atomic radius increases
- Shielding stays the same

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20
Q

What 2 elements deviate from the general trend in ionisation energies across period 2? Explain why

A

Boron: 1s2 2s2 2p1
- outer electron removed from 2p sub-shell
- 2p sub-shell is higher in energy
- so less energy required to remove outer electron

Oxygen: 1s2 2s2 2p4
- outer electron removed from 2p sub-shell from a paired orbital
- less energy required to remove outer electron
- due to electron pair repulsion

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21
Q

What is the trend in ionisation energies down a group? Explain why

A
  • Decrease in ionisation energies
  • Increase in atomic radius
  • Due to increased shielding
  • Weaker attraction between outer electrons and nucleus
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22
Q

What are the 3 factors that influence ionisation energies? Explain why/how

A

N D S
Nuclear charge:
- Increase in nuclear charge
- stronger attraction between outer electrons and nucleus
- Increases ionisation energies

Distance from nucleus/atomic radius:
- decrease in atomic radius
- stronger attraction between outer electrons and nucleus
- increases ionisation energies

Shielding
- decreased shielding
- stronger attraction between outer electrons and nucleus
- increases ionisation energies

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23
Q

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

A
  • General increase
  • Increase in nuclear charge
  • Decrease in atomic radius
  • Same shielding
  • So greater attraction between outer electrons and nucleus
24
Q

What 2 elements deviate from the general trend of 1st ionisation energies in period 3?

A

Aluminium and Sulfur

25
Q

Explain why Aluminium has a lower 1st ionisation energy than Magnesium

A

Al: 1s2 2s2 2p6 3s2 3p1
Mg: 1s2 2s2 2p6 3s2

  • Outer electron of Al is taken from the 3p sub-shell whereas the outer electron of Mg is taken from the 3s sub-shell
  • 3p sub-shell is higher in energy than the 3s sub-shell therefore less energy is required to remove the outer electron
26
Q

Explain why Sulfur has a lower 1st ionisation energy than Phosphorous

A

S: 1s2 2s2 2p6 2s2 3p4
P: 1s2 2s2 2p6 3s2 3p3

  • Outer electron of Sl is taken from a 3p paired orbital whereas the outer electron of P is taken from a 3p unpaired orbital
  • Less energy is required to remove the electron from S due to electron pair repulsion
27
Q

State and explain the trend in atomic radius down a group

A
  • Atomic radius increases
  • Due to increase in shielding
28
Q

What is meant by atomic number?

A

Equal to the number of protons

29
Q

What is meant by mass number?

A

Equal to the number of protons and neutrons combined

30
Q

What is meant by an isotope?

A
  • Atoms with the same number of protons and electrons but a different number of neutrons
31
Q

Why do isotopes of the same element have the same chemical properties?

A

Because they have the same electron configuration

32
Q

Describe how a time of flight mass spectrometer works

A
  • Ionisation: particles gain a positive charge by undergoing electrospray/electron impact ionisation
  • Acceleration: Positively charged ions attracted to negatively charged plate
  • Detection: As each ion hits the detector, an electron is gained which generates a current
  • current proportional to the relative abundance (number of each type of ion)
  • Data analysis: signal from detector passed onto computer. Mass spectrum generated
33
Q

Describe electron impact ionisation

A
  • Sample is vaporised
  • High energy electrons fired from an electron gun
  • Knocking off an electron off each molecule, forming 1+ ions
34
Q

What is the equation of ionisation of CH4 after undergoing electron impact ionisation?

A

CH4 (g) —> CH4+ (g) + e-

35
Q

Describe electrospray ionisation

A
  • Sample is dissolved in a volatile solvent
  • Injected through a fine hypodermic needle
  • Needle is connected to a positive terminal of high voltage
  • Particles ionised by gaining a proton
36
Q

Why are sample particles ionised?

A
  • So they can accelerate towards the negatively charged plate
  • So a current is generated when they hit the detector
37
Q

How is the ion accelerated?

A
  • Positive ions are attracted to a negatively charged plate
  • All ions have the same KE
38
Q

How are the ions separated in the flight tube?

A
  • Lighter ions (smaller m/z ratio) move ahead of heavier ions (larger m/z ratio)
  • Lighter ions travel at faster speed
39
Q

How are the ions detected?

A
  • Ion hits detector
  • Each ion gains electron
  • Generates a current
  • Size of current proportional to ion abundance
40
Q

What is the equation for KE?

A

KE = 1/2mv2

41
Q

What is the equation for speed/distance/time

A

v = d/t

42
Q

Formula to calculate relative atomic mass?

A

(mass 1 x abundance 1) + (mass 2 x abundance 2) + (mass n x abundance n) / total abundances

43
Q

State two features of todays atomic structure model that is not shown in Rutherford/plum pudding model

A
  • Nucleus containing protons and neutrons
  • Electrons arranged in different energy levels/orbitals
44
Q

Define the term relative atomic mass

A
  • Average mass of an atom of an element
  • Compared to 1/12th the mass of on atom of carbon-12
45
Q

What is the electron configuration of an atom with only two unpaired electrons?

A - 1s2 2s2 2p3
B - 1s2 2s2 2p4
C - 1s2 2s2 2p6 3s2 2p5
D - 1s2 2s2 2p6 3s2 2p6 4s1 3d5

A

B - 1s2 2s2 2p4

46
Q

State in terms of fundamental particles, one similarity and one difference between atoms of Cr50 and Cr53

A

Similarity:
same number of protons

Difference
different number of neutrons

47
Q

Give two reasons why it is necessary to ionise isotopes before they can be analysed in a TOF mass spectrometer

A
  • positive ions accelerated by electric field
  • Ions hit detector to create a current
48
Q

Explain the pattern in first ionisation energies of the elements from lithium to neon

A
  • 1st IE increases (generally)
  • Increase in nuclear charge
  • Same shielding
  • stronger attraction between outer electrons and nucleus

Deviation from Be –> B
- B has lower 1st IE
- Outer electron in 2p which is higher in energy than 2s

Deviation from N –> O
- O has lower 1st IE
- 2 paired electrons in 2p
- electron pair repulsion

49
Q

State and explain trend in 1st ionisation energies of elements in group 2 from magnesium to barium

A
  • General decrease
  • Ions get bigger
  • Weaker attraction of ion to lost electron
50
Q

Describe how ions are formed in TOF mass spectrometer

A

Describe electrospray/electron impact

51
Q

Outline how TOF mass spectrometer is able to separate two species to give two peaks

A
  • positively charged ions accelerated by electric field
  • All ions have same KE
  • ions with lower m/z travel faster
  • ions with lower m/z reach detector first
52
Q

suggest why the Mr calculated is different to the one on the periodic table

A

other isotopes present

53
Q

state how relative abundance is determined in TOF spectrometer

A
  • each ion gains electron as it hits detector
  • relative abundance depends on size of current
54
Q

give two reasons why it is necessary to ionise isotopes of chromium before they can be analysed by TOF mass spectrometer

A
  • so they can be accelerated to negative plate
  • ions create current when hitting detector
55
Q

identify period 3 element with highest SECOND ionisation energy

A

sodium

56
Q

explain why atomic radius decreases across period 3

A
  • increase in nuclear charge
  • similar shielding
57
Q

Identify the element in Period 3, from sodium to chlorine, that has the highest electronegativity.

A

Chlorine

AQA - A level Chemistry (25 decks)

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