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A-Level Chemistry > Atomic Structure > Flashcards

Atomic Structure Flashcards

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1
Q

What is Relative Atomic Mass? (Ar)

A

Ar is the average mass of an atom of an element on a scale where an atom of carbon-12 is exactly 12

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2
Q

What is Relative Isotopic Mass?

A

This is the mass of an atom of an isotope of an element on a scale where an atom of carbon-12 is exactly 12

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3
Q

What is Relative Formula Mass?, How do you find it? and What is it used for?

A

This is the average mass of a formula unit on a scale where an atom of carbon-12 is exactly 12 (add up all Ar of ions in the formula), this is used for ionic compunds

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4
Q

What is Relative Molecular Mass? (Mr) and How do you find it?

A

Mr is the average mass of a molecule on a scale where an atom of carbon-12 is exactly 12
Mr = (isotopic mass x percentages)/total percentages

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5
Q

Describe the Dalton atomic model

A
  • Solid sphere
  • Each element made up of one type of atom only
  • Learn diagram
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6
Q

Describe the JJ Thompson atomic model

A
  • Plum Pudding model
  • discovered the electron (negative and small)
  • Negative electrons (plums) and positive pudding
  • Learn diagram
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7
Q

Describe the Rutherford atomic model

A
  • Discovered the nucleus (tiny, massive and positive)
  • Gold Foil experiment
  • Most of the atom is empty space
  • Alpha particles shot in and most get through but some are deflected (by nucleus)
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8
Q

Describe the Bohr atomic model

A
  • Put electrons in shells
    MASS CHARGE
    P 1 +1
    E 1/2000 -1
    N 1 0
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9
Q

How are ions formed and what are they?

A

Formed by gaining or losing electron and they are atoms with different numbers if protons and electrons

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10
Q

How do you work out the number of neutrons?

A

neutrons is mass number minus atomic number

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11
Q

Why are atoms neutral?

A

They have the same number of protons as electrons

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12
Q

What is an isotope?

A

An isotope of an element are atoms with the same number of protons but different numbers of neutrons

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13
Q

What decides the chemical properties an element?

A

Number and arrangement of electrons

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14
Q

Why do isotopes have the same chemical properties but slightly different physical properties?

A
  • Same chemical properties because they have the same configuration of electrons
  • They have slightly different physical properties because they depend on the mass of the atom
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15
Q

What is the atomic number?

A

It is the number of protons and it identifies the element

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16
Q

What is the mass number?

A

It is the total number of protons and neutrons in the nucleus

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17
Q

What are the symbols for mass number and atomic number?

A

Atomic number = Z

Mass number = A

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18
Q

Describe group 0 elements

A

They have completely filled S and P sub shells (don’t gain, lose or share electrons). This makes them inert

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19
Q

Describe S block elements (Group 1 and 2)

A

They have 1 or 2 outer electrons, they are easily lost to form positive ions with an inert gas configuration

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20
Q

Describe P block elements (Group 5, 6 and 7)

A

They gain 1, 2 or 3 electrons to form negative ions with an inert gas configuration

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21
Q

What can Group 4-7 elements form?

A

Covalent bond because they can share electrons

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22
Q

What do electrons have in relation to electron shells?

A

They have fixed energies and they move around the nucleus in shells or energy levels

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23
Q

What are each shell given? and When is this higher?

A

a principal quantum number (further from nucleus mean higher principal quantum number and higher energy)

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24
Q

What do all electrons in the same shell have?

A

The same energy

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25
What are the 4 types of sub shells?
S, P, D and F
26
What are shells divided into?
Sub-shells
27
What do different shells have?
different numbers of subshells which each have different energy
28
What do each type of sub shells have?
different numbers of orbital
29
How many electrons can an orbital hold and how many orbitals does each type of sub shell have?
- Orbitals can hold 2 electrons - S sub shells have 1 orbital so hold 2 electrons - P sub shells have 3 orbitals so hold 6 electrons - D sub shells have 5 orbitals so hold 10 electrons - F sub shells have 7 orbitals so hold 14 electrons
30
What is sub shell notation and describe the different parts of it?
EG. 1s2 2s2 2p6
31
Learn arrow in boxes diagrams and why are the arrows in the boxes in opposite directions
The boxes represent orbitals and the arrows are opposite because the electrons are spinning in opposite directions
32
Learn energy level digrams, What do they show?
they show energy of electrons in different orbitals, as well as the number of electrons and the arrangement
33
What are the rules for sub shells?
- Electrons fill the lowest energy sub shells (4s before 3d) - Electrons fill orbitals in a sub shells singly before they share an orbital - With ions, highest energy levels leave first but 4s leaves before 3d
34
What are the two exception for these rules and why are they like this?
- Chromium - 1s2 2s2 2p6 3s2 3p6 4s1 3d5 - Copper - 1s2 2s2 2p6 3s2 3p6 4s1 3d10] - They both only have one electron in the 4s sub shell because it makes them more stable
35
What is the first ionisation energy? and Write an example equation
This is the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions Eg. O(g) --> O+(g) + e-
36
What are some important points in relation to ionisation energies?
- Refer to 1 mole of atoms rather than to a single atom - Lower ionisation energy means its easier to form +ions - Use state symbols because ionisation energies are measure for gaseous atoms
37
What are the factors that affect ionisation energy?
- Nuclear Charge (more protons = more positive charge so electron attraction is stronger) - Distance from nucleus (attraction falls with distance because electrons have less attraction) - Shielding (as the number of e- between outer shell and nucleus increase, outer electron has less attraction. This is due to the number of inner shells)
38
What is the second ionisation energy? and Write an example equation
This is the energy needed to remove an electron from each ion in 1 mole of gaseous 1+ ions Eg O+(g) --> O2+(g) + e-
39
Why is second ionisation energy greater than the first?
- Removing electron from an ion (stronger attraction) | - Electron configuration has changed
40
What is a successive ionisation energy?
You can remove all electrons so there is just a nucleus, each time there is a successive ionisation energy
41
What is the equation for successive ionisation energies?
X(n-1)+(g) --> Xn+(g) + e-
42
What is the trend of ionisation energies down a group?
Distance from nucleus and shielding increase so it is easier to remove electron, even though nuclear charge increases
43
What is the general trend of ionisation energies across a period?
Left to right ionisation energies increase because distance of electrons from nucleus is similar and shielding is the same but nuclear charge increases
44
Why are the two dips across a period due to?
- sub shell dip | - Electron pair repulsion dip
45
What is the sub shell dip between Mg and Al due to?
Even though charge increases, Al's ionisation energies is lower because Al has more shielding and its outer electron is further from nucleus than Mg's
46
What is the electron pair repulsion dip between P and S due to?
The outer electron for S is easier to remove than P's because the outer electron from S comes from an orbital with 2 electrons (which repel each other), meaning less energy is needed for the first ionisation energy of S. Even though distance is the same and nuclear charge increases
47
Learn the diagrams for the increase ionisation energy throughout electrons in different shells
Describe what they mean
48
Why are there big jumps in ionisation energies between shells?
This is because electrons are closer to the nucleus
49
Why are there successive ionistion energies within each shell?
this is because they are removed from an increasingly positive ion, because there is less repulsion amongst electrons (stronger)
50
Describe the method for electron impact ionisation (give the equation)
- Sample is vaporized - High energy electron is fired at the sample - Knocking one electron from each particle forming 1+ ions (called the molecular ion) - X(g) + e- --> X+(g) + 2e-
51
What does the molecular ion do when it is detected?
breaks into small fragments that are detected
52
What is an electron gun?
Hot wire filament with a current
53
What sort of elements is electron gun ionisation used for?
elements with low formula mass
54
Describe the method for electrospray ionisation (give the equation)
- Sample is dissolved in a volatile solvent - Then injected through a fine hypodermic needle to give a fine mist - Tip of the needle is attached to a positive terminal (high voltage) - particles ionised by giving a H+ ion from the solvent as they leave the needle forming XH+ ions - X(g) + H+ --> XH+(g)
55
What elements is electrospray ionisation used for?
elements with higher molecular mass (proteins)
56
What is electrospray ionisation also called and what rareley happens?
Known as 'soft' ionisation and fragmentation rarely occurs
57
Describe acceleration in a mass spectrometer
- positive ions are accelerated using an electric field | - so all the ions have the same kinetic energy
58
What does velocity of the ions depend on?
- Mass of each particle (lighter = faster)
59
Learn the equations for acceleration and what are the units for each part?
``` KE = 1/2MV² V = square root of (2KE/M) KE = J M = mass in kg V = velocity in m/s ```
60
What does time of flight depend on?
Depends on velocity and so mass
61
What do the + ions travel through?
Travel through the hole in the negative plate and into the tube
62
What is time of flight proportional to?
- the square root of the mass of an ion | - Lighter = fast = reach detector quicker
63
What does d stand for?
length of tube
64
What are the equations for time in a mass spectrometer?
- T = d/v | - T= d x square root of (M/2KE)
65
Describe how ions are detected
- positive ion hits negative detector and are discharged by gaining an electron - Generates a movement of electrons and a current is measured - Size of current gives a measure of the number of ions hitting the plate
66
How do you work out Ar?
Ar = (mass of all isotopes x abundance of each isotope)/ abundance of all isotopes
67
How is the mass spectrum produced? And what does the mass spectrum show?
- computer uses data to produce mass spectrum | - Shows mass to charge (m/z) ratio and abundance of each ion that gets to the detector
68
What is M/Z in electrospray ionisation?
It is effectively mass
69
What is the signal greatest with the greatest M/Z value from? And what does this value give? (electron impact)
The molecular ion and it gives the relative molecular mass
70
Why would there be other peaks around the molecular peak? (electron impact)
This is due to different isotopes
71
Why would there be peaks at lower M/Z values? (electron impact)
This is due to fragments

A-Level Chemistry (8 decks)

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