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chemistry > Atomic Sturcture > Flashcards

Atomic Sturcture Flashcards

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1
Q

What is the relative mass of a proton, neutron and an electron?

A

Proton 1
Neutron 1
Electron 1/1836

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2
Q

What is the relative charge of a proton neutron and electron?

A

Proton +1
Neutron 0
Electron -1

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3
Q

What is the mass number? (A)

A

The sum of the number of protons and neutrons

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4
Q

What is atomic number? (Z)

A

The number of protons in an atom

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5
Q

What happens if the number of protons changes?

A

The element / atom also changes

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6
Q

Define an isotope

A

Isotopes are atoms of the same elements with the same number of protons but a different number of neutrons

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7
Q

Define chemical reactivity
Why do isotopes have the same chemical reactivity?

A

They have the same chemical reactivity (the way they react) because they have the same number of electrons therefore they have the same electronic structure (arrangement of electrons) and atoms react by losing it gaining electrons

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8
Q

Why do isotopes have different physical properties?

A

Isotopes have different physical properties because the atoms have different masses

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9
Q

What are 3 physical properties?

A

Melting point
Boiling point
Solubility

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10
Q

Give the worded definition of relative atomic mass

A

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

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11
Q

Give the equation definition of relative atomic mass

A

Average mass of an atom x12 divided by mass of one atom of carbon 12

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12
Q

Why is the Ar of an element infrequently a whole number? (Atomic mass)

A

The ar takes into account the average mass of all the isotopes including their abundances

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13
Q

How do we define relative isotopic mass, molecular mass or formula mass using the atomic mass definition?

A

Substitute in mass of an isotope, molecule or compound or ion in the place of mass of one atom

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14
Q

What is a mass spectrometer?

A

An instrument used to determine the abundance and the mass of each isotope in an element which allows us to determine the relative atomic mass and the relative molecular mass of molecules

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15
Q

What are the 4 steps of mass spectrometry?

A

Ionisation
Acceleration
Separation (ion drift)
Detection

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16
Q

What is ionisation in mass spectrometry?

A

Producing a positive ion

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17
Q

Describe the process of ionisation by electron impact

A
  1. The sample is vaporised and injected into the mass spectrometer which has a rubber part for the injection
  2. High energy electrons are fired at the sample as it diffuses across the ionisation area
  3. The electrons collide with the sample atoms as they are attracted to a positive plate opposite to the electron gun, the high speed of the electrons causes a strong force so an electron is knocked off from the sample atoms leaving them as positive ions with a positive charge
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18
Q

Why is the rubber part on the mass spectrometer important?

A

If reseals itself when the gas is injected into it to stop the gas from escaping

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19
Q

Where do the electrons come from in electron impact ionisation?

A

They come from an electron gun which is a coil of hot wire filament that has a current running through it which allows it to release electrons

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20
Q

What is a vacuum?
Why does the ionisation area need to be a vacuum?

A

Area with no air or other particles present
It needs to be a vacuum because if other particles were present they would also be ionised which would cause them to be detected by the detector therefore producing contaminated results

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21
Q

What is the general electron impact ionisation equation?
What is something you must always state and why?

A

X (g) —> X+ (g) + e-

The gaseous state as the sample is always vaporised

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22
Q

Describe the process of ionisation by electrospray ionisation?

A
  1. The sample is dissolved into a volatile solvent then injected into a hypodermic needle to give a fine aerosol mist
  2. The particles are ionised by gaining a proton form the solvent so they leave the needle producing XH+ ions.
  3. The solvent evaporates away with XH+ ions are attracted towards the negative acceleration plates
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23
Q

What is a volatile solvent?

A

A solvent that easily turns into a gas
Volatile - how easily something turns into a gas

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24
Q

What are 2 examples of volatile solvents?

A

Methane and Water

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25
Q

What is the hypodermic needle attached to?

A

It is attached to a positive terminal of a high voltage power supply

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26
Q

What is a XH+ ion?

A

An ion with a single positive charge and a mass of the Mr + 1

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27
Q

What is the general electrospray ionisation equation?

A

X (g) + H+ —> XH+ (g)

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28
Q

Describe the acceleration stage of mass spectrometry

A
  1. The positive ions move into the accelerator area by their attraction to the negative plates
  2. The negative plates produce an electric field which gives the particles kinetic energy
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29
Q

What is the same for all the particles in the acceleration area and what is different?

A

They all have the same kinetic energy however they all have different velocities because of their different masses

30
Q

What is the equation for kinetic energy? (Units included?

A

1/2mv^2

Kinetic energy - Joules
Mass in kg
velocity in m/s

31
Q

What are the 2 equations for velocity?

A

Velocity = distance / time
Velocity in m/s
Distance in metres
Time in seconds

Velocity = square root of 2KE / mass
Velocity m/s
KE in joules
Mass in kg

32
Q

Describe the drift region / ion drift stage of mass spectrometry?

A
  1. The positive ions travel into a region called the flight tube where the separation occurs
  2. The particles move at different speeds so they reach the detector at different times which is used to identify the isotopes (heavier ions move slower)
33
Q

What is the relation between the time of flight and the mass of an ion?

A

The time of flight is proportional to the square root of the mass of an ion

34
Q

Describe the detection stage of mass spectrometry?

A
  1. The positive ions hit a negative charged plate
  2. The positive ions are discharged by gaining electrons form the plate
  3. This generates an electric current ( due to flow of electrons ) which can be measured
35
Q

What is the size of the current used to measure? (2)

A

The size of the current gives a measure of the number of ions hitting the detector
It is also proportional to the abundance so the number of ions of each isotope hitting the plate

36
Q

What is the m/z value?

A

The mass to charge ratio

37
Q

What can mass spectrometry be used for and how?

A

It can be used to identify elements because each element has its own characteristic pattern

38
Q

Why do diatomic elements with 2 isotopes have a complex mass spectra?

A

They contain peaks for both of the separate ions and the molecules they form which results in 5 peaks

39
Q

What is the equation for relative atomic mass from isotopic abundances?

A

Sum of (mass of isotope x abundance) / sum of abundances

40
Q

What is the aufbaw principal?

A

Electrons will always enter the lowest energy sub - level available and will not enter higher energy levels until those below them are full.

41
Q

What is the order of filling?

A

1S 2S 2P 3S 3P 4S 3D 4P 5S

42
Q

Why does the 4S sub level fill before the 3D?

A

The sub levels increase in energy levels and 4S is at a lower energy than 3D because it can hold fewer electrons

43
Q

What is the maximum electron each sun level holds?

A

S - 2
P - 6
D - 10
F - 14

44
Q

What are orbitals?

A

They are regions of space where there is a 95% probability of finding and electron. ( electrons move all the time in a specific shape - shape of orbital )

45
Q

How are orbitals determined?
How many electrons does one orbital hold?

A

They are determined by measuring electron density around the nucleus
2 electrons maximum

46
Q

How many orbitals does the S sub level have?
How many electrons does it hold?
What is the shape of the orbital?

A

1 orbital
2 electrons maximum
Spherical shape

47
Q

How many orbitals does the P sub level have?
How many electrons does it hold?
What is the shape?

A

3 orbitals
6 electrons maximum
X direction, y direction and diagonal (8)

48
Q

How many orbitals and electrons does the d sub level hold / have ?
How many electrons and orbitals does the f sub level hold / have ?

A

D 5 orbitals and 10 electrons
F 7 orbitals and 14 electrons

49
Q

What does a spin diagram show?

A

How orbitals are filled

50
Q

What are orbitals and electrons represented by in spin diagrams?

A

Orbitals - squares
Electrons - half arrows pointing up or down (direction is the spin of electron)

51
Q

What is Hund’s rule?

A

Electrons occupy all empty orbitals within a sub level before they start to form pairs in orbitals

52
Q

Why are 4S electrons lost before 3D electrons?

A

Electrons are lost from the highest sub - levels first and when the 4S sub level gains electrons it gains energy and jumps above the 3d sub level

53
Q

Why don’t copper and chromium follow the general rule of order of filling?

A

They have greater stability when they have a full ( 2 electrons in each orbital) of half full ( 1 electron in each orbital ) D sub level so they only have one electron in 4S (4S1)

54
Q

How did you write short hand electronic configurations?

A

Go back from your element in order of atomic number until you reach your first noble gas
(Symbol of noble gas) followed by the left over electronic configuration from the original element

55
Q

What is ionisation?

A

The process in which atoms ose or gain electrons and become ions

56
Q

What is the first ionisation energy?

A

The energy required to remove one mole of electrons from one mole of gaseous atoms to form one mole of gaseous atoms with a +1 charge

57
Q

How do you define the nth ionisation equation?

A

The energy required to remove one mole of electrons from one mole of gaseous ions with a (n-1) + charge to from one mole or gaseous ions with an n+ charge

58
Q

How do you write the nth ionisation equation?

A

X(g) (n-1)+ —> X(g) n+ + e-

59
Q

What are the 3 factors that affect ionisation energy?

A

The energy of the electron being removed
The size of the nuclear charge
The shielding effect by electrons in filled inner shells

60
Q

What is the energy of the electron being removed?
How does this affect ionisation energy? (2)

A
  • The average distance of the electron form the nucleus
  • If the electron is in a high energy sub level then it is further away from the nucleus so it has a weaker attraction from the nucleus so a lower ionisation energy is required to remove the electron
  • if the electron is in a low energy sun level then it is closer to the nucleus therefore has a stronger attraction to it so a higher ionisation energy is required to remove the electron
61
Q

How is the size of the nuclear charge determined?
How does it affect ionisation energy?

A
  • The size or the nuclear charge is determined by how many protons the atom has
  • The more protons an atom has the higher it’s nuclear charge therefore it has a stronger attraction to the electrons so a higher ionisation energy is required to remove them
62
Q

What is the shielding effect by electrons in filled inner shells?
How does this affect ionisation energy?

A
  • When electrons are in a full shell so they shield outer electrons from the nucleus
  • The more electrons that there are shielding the we are the attraction between the outer electrons and the nucleus so a lower ionisation energy is required to remove the electrons
63
Q

What is successive ionisation energy?

A

It is the amount of energy required to lose each electron from an atom after one electron has already been lost which results in each electron having different ionisation energies

64
Q

Why does the successive ionisation energy increase each time an electron is removed?

A

It increases because the positive charge of the ion increases so the electrons get a stronger attraction to it so a higher energy is required to remove the electrons

65
Q

How can you tell the period number from successive ionisation graphs?

A

The number of jumps in ionisation energy + 1

66
Q

How can you tell the group number form successive ionisation graphs?

A

It is the number of electrons removed before the first big jump in ionisation energy

67
Q

What do large jumps in ionisation energy tell us?

A

They tell us where electrons are being removed from a lower energy sub level as the distance between electrons and the nucleus decreases which results una stronger attraction so more energy is required to remove the electrons

68
Q

What are 3 trends down a group?
How does this affect ionisation energy?

A

There is more shielding
A higher number of protons
The distance between outer electrons and nucleus increases ( period number increases )

The first 2 have opposite effect so cancel each other out
Last one causes the first ionisation energy to decrease as you go down a group because a larger distance = weaker attraction so less energy required to remove electrons

69
Q

What are 4 trends across a period? How do 3 of them affect ionisation energy?

A

The distance of outer electrons from the nucleus remains the same (NO effect)
The shielding effect is almost constant (NO effect)
The nuclear charge increases so as you go across a period the ionisation energy increased because higher charge = stronger attraction so more energy needed to remove electrons

The atomic radius decreases because the nuclear charge increases so the electrons become more attracted which pulls in both electrons and shells towards the nucleus

70
Q

What do dips in ionisation energy graphs across a period tell us?

A

They show that the atom with the lower ionisation energy has its outer electrons in a higher sub level which means they are further away from the nucleus so they have a weaker attraction = less energy to remove

chemistry (23 decks)

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