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Chemistry > Unit 1: Section 1: Atomic Structure > Flashcards

Unit 1: Section 1: Atomic Structure Flashcards

1
Q

Nuclear symbol for mass number, atomic number and element symbol

A

Mass number: A
Atomic number: Z
Element symbol: X

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2
Q

What are the four basic principles that Niels Bohr proposed for his model of the atom

A

Electrons only exist in fixed orbitals
Each shell has a fixed energy
When an electron moves between shells electromagnetic radiation is emitted or absorbed
Because the energy of shells is fixed, the radiation will have a fixed frequency

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3
Q

What is relative atomic mass

A

The average weighed mass of one atom compared to 1/12th the mass of one atom of carbon 12

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4
Q

What is relative isotopic mass

A

The relative isotopic mass is the mass of an isotope relative to 1/12th of the mass of a carbon-12 atom

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5
Q

What is relative formula mass

A

The average mass of a formula unit on a scale where an atom of carbon-12 is exactly 12

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6
Q

How do you work out the relative formula mass

A

Add up the relative formula mass of all the ions that make the compound

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7
Q

What is a mass spectrometer

A

A machine used to analyse elements or compounds

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8
Q

What information can you derive from mass spectrometry

A

Relative atomic mass
Relative abundance of its isotopes
Relative molecular mass of a molecule

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9
Q

What are the four things that happen when a sample enters a time of flight mass spectrometer

A

Ionisation
Acceleration
Ion drift
Detection

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10
Q

Explain the ionisation stage of time of flight mass spectrometry

A

Sample needs to be ionised before it enters the spectrometer
Two ways to do this is :
- Electrospray ionisation - in this method the sample is dissolved
in a solvent and pushed through a small nozzle at a high
pressure. High voltage is applied to it so each particle gains a
H+ ion. The solvent is then removed leaving a gas made up of
positive ions
- Electron impact ionisation - sample is vaporised and an
electron gun is used to fire high energy particles at it. This
knocks one electron off each particle, so they become 1+ ions

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11
Q

Explain the acceleration stage in time of flight mass spectrometry

A

Positive ions are accelerated by negatively charged electric field
Lighter ions experience greater acceleration because they experience the same kinetic energy as the heavier ions but they weigh less

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12
Q

Explain the ion drift stage in time of flight mass spectrometry

A

The ions enter a region with no electric field
They drift through it at the same speed as the speed in the electric field
The lighter ions will therefore drift at a quicker speed

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13
Q

Explain the detection stage in time of flight mass spectrometry

A

The lighter ions reach the ion detector quicker then the heavier ions
Detector detects the current created when the ions hit it and records how long they took to pass through the spectrometer. This data is then used to calculate the mass/charge values needed to produce a mass spectrum

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14
Q

What are the y and x axis in a mass spectrum

A

y - % abundance
x - mass/charge

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15
Q

Explain the relationship between the mass/charge ratio and the relative mass of each isotope when the sample has been ionised by electron impact ionisation

A

Since one electron is being knocked off and turning the sample into +1 ions the mass/charge ratio will be the same as the relative mass of that isotope

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16
Q

Explain the relationship between the mass/charge ratio and the relative mass of each isotope when the sample has been ionised by electrospray ionisation

A

Since H+ ions are added for each particle to form +1 ions the mass/charge ratio of each peak would be one unit greater than the relative mass of each isotope

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17
Q

How do you work out how many isotopes of the element are present in the sample

A

Count the amount of peaks in % abundance

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18
Q

How to calculate the relative atomic mass from a mass spectrum

A

Multiply the relative isotopic abundance (read y axis) by the mass (read x axis) and divide by 100

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19
Q

How do you calculate the relative molecular mass of a molecular ion from a mass spectrum

A

Find the mass/charge ratio and it is the same as that value

20
Q

What is a principal quantum number and explain it’s relationship to the nucleus

A

A measurement of how far a shell is from a nucleus
The further a shell is from the nucleus the larger the principal quantum number is

21
Q

Explain the relationship between the distance of the shell from the nucleus and the amount of energy

A

The further a shell is from the nucleus the higher it’s energy

22
Q

Name the four different sub shells you can have

A

s, p, d, f

23
Q

List the different sub shells in each shell up to four shells

A

1st : 1s
2nd : 2s, 2p
3rd : 3s, 3p, 3d
4th : 4s, 4p, 4d, 4f

24
Q

What are the different number of orbitals in each sub-shell and what are the maximum electrons that each sub shell can hold

A

s : 1 Max electrons : 2
p : 3 Max electrons : 6
d : 5 Max electrons : 10
f : 7 Max electrons : 14

25
Q

What are the three rules when working out electron configuration

A

Rule 1 : Electrons fill up the lowest energy sub-shells first
Rule 2 : Electrons fill orbitals in a sub-shell singly before they start sharing
Rule 3 : For the configuration of ions from the s and p blocks of the periodic table just add or remove the electrons to or from the highest energy occupied sub-shell

26
Q

What is the rule regarding the s and d sub-shells

A

s fills and empties before d

27
Q

Define relative molecular mass

A

The average weighed mass of one molecule compared to 1/12th the mass of one atom of carbon 12

28
Q

Equation for electrospray

A

M(g)+ H^+(g) –> MH^+(g)

29
Q

What is the anomaly to electron configuration

A

Chromium and Copper
They both donate one of their electrons to the 3d sub shell

30
Q

What is the first ionisation energy

A

The first ionisation energy 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

31
Q

Write the equation for the first ionisation of oxygen

A

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

32
Q

What state symbol should be used when writing equations for ionisation energy

A

(g)
Because ionisation energies are measured for gaseous atoms

33
Q

What is the correlation between ionisation energy and the reactivity

A

The lower the ionisation energy the easier it is to form a positive ion

34
Q

What does a high ionisation energy mean

A

There’s a high attraction between the electron and the nucleus, so more energy is needed to remove the electron

35
Q

What are the three things that affect ionisation energy

A

Nuclear charge:
- The more protons in the nucleus the stronger the attraction
between the nucleus and the electrons
Distance from nucleus:
- Attraction falls very rapidly with distance between the nucleus
and the electron
Shielding:
- As the number of electrons between the outer electron and the nucleus increases the attraction decreases

36
Q

What is second ionisation energy

A

The second ionisation energy is the energy needed to remove an electron from each ion in 1 mole of gaseous 1+ ions

37
Q

Write the equation for the second ionisation energy of oxygen

A

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

38
Q

Why is the second ionisation energy always higher than the first

A

Because the atom becomes a positive ion so the attraction is stronger so more energy is needed to remove it
It will also experience less shielding
It is also closer

39
Q

Write the general equation for successive ionisation

A

X(n-1)+ (g) -> Xn+ (g) + e-

40
Q

what is the equation for the fifth ionisation energy of oxygen

A

O4+ (g) -> O5+ + e-

41
Q

Describe the ionisation energy trends going down group 2

A

The first ionisation energy decreases

42
Q

What is the general trend for ionisation energy when you move across a period

A

To increase
Number of protons increase so attraction is stronger

43
Q

What are the two exceptions to the ionisation energy trend across periods

A

Mg and Al
P and S

44
Q

Explain why Mg is higher in ionisation energy than Al

A

Al’s outer electron is in a 3p orbital rather than a 3s
3p is higher in energy than the 3s orbital so the electron (on average) is found further from the nucleus
3p orbital has additional shielding provided by the 3s electrons

45
Q

Explain why P is higher in ionisation energy than S

A

In P the electron is removed from a singly-occupied shell
In S it is being removed from a shell with two electrons
The repulsion from two electrons in the same orbital means it is easier to be removed so it has lower ionisation energy

Chemistry (9 decks)

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