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AQA Chemistry > 1.1 Atomic Structure > Flashcards

1.1 Atomic Structure Flashcards

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1
Q

relative charge of a proton

A

+1

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2
Q

relative charge of a neutron

A

0

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3
Q

relative charge of an electron

A

-1

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4
Q

relative mass of a proton

A

1

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5
Q

relative mass of a neutron

A

1

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6
Q

relative mass of an electron

A

1/1836

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7
Q

what is the atomic number? (Z)

A

number of protons

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8
Q

what is the mass number (A)

A

total number of protons and neutrons

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9
Q

how to calculate number of neutrons

A

mass number - atomic number

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10
Q

what holds an atom together

A

the electrostatic attraction between the positive nucleus and the negatively charged electrons

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11
Q

what are isotopes?

A

atoms of the same element that contain the same number of protons and electrons but different number of neutrons

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12
Q

why do isotopes of the same element display the same chemical characteristics?

A

they have the same number of electrons in their outer shells

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13
Q

what is the physical difference of isotopes?

A

the number of neutrons and therefore the mass

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14
Q

what is relative atomic mass

A

average mass of an isotope compared to C-12

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15
Q

How to calculate the relative atomic mass (Ar)

A

(relative abundance of isotope 1 x mass of isotope 1) + (relative abundance of isotope 2 x mass of isotope 2) etc / 100

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16
Q

what is mass spectrometry used for?

A
  • accurate determination of the Ar of an element, based on the abundance and mass of its isotopes
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17
Q

4 key stages of time of flight mass spectrometry

A
  • ionisation
  • acceleration
  • ion drift
  • detection
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18
Q

what are the two key methods of ionisation in mass spectrometry

A

electron impact
electrospray ionisation

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19
Q

which ionisation method is used for substances with lower molecular mass?

A

electron impact

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20
Q

how is a sample ionised in electron impact ionisation

A

the sample is vaporised and bombarded with high energy electrons fired from an electron gun

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21
Q

what does the electron gun do

A

it emits electrons as a current runs through a hot wire filament

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22
Q

what is the result of the bombardment of electrons

A

an electron is knocked off each particle, forming a 1+ ion.
X (g) → X+ (g) + e-

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23
Q

what are the ions formed in electron impact ionisation called?

A

molecular ions / M+ ions

24
Q

what happens to the molecular ions after they are formed?

A

they are attracted to a negatively charged plate and accelerated through the mass spectrometer

25
Q

what occurs after the molecular ion is formed

A

the molecular ion can fragment into smaller ions, which are also detected

26
Q

which ionisation method is typically used for substances with higher molecular mass?

A

electrospray ionisation

27
Q

what is a characteristic of electrospray ionisation that differs from electron impact?

A

fragmentation is unlikely to happen - it is considered a soft ionisation technique

28
Q

how is the sample prepared for electrospray ionisation

A

the sample is dissolved in a volatile solvent and injected into the mass spectrometer

29
Q

what happens when the sample is injected in electrospray ionisation

How are they ionised + what does it produce

A

it produces a fine mist or aerosol, and the particles are ionised by gaining a proton from the solvent

30
Q

what happens to the XH+ ions after they are formed in electrospray ionisation?

A

the solvent evaporates and the XH+ ions are attracted to a negatively charged plate, accelerating them through the mass spectrometer.

31
Q

what happens once the sample is ionised

A

the 1+ ions are accelerated using an electric field.

32
Q

what is a key principle regarding the kinetic energy of 1+ ions?

A

all 1+ ions are accelerated to have the same kinetic energy.

33
Q

how does the mass affect the velocity of 1+ ions?

A

lighter ions move faster, whilst heavier ions move slower.

34
Q

what happens to the 1+ ions after they are accelerated?

A

they pass through a hole in the negatively charged plate and move into a flight tube

35
Q

what does the time of flight of each 1+ ion depend on?

A

their velocity

36
Q

what happens to the 1+ ions after they pass through the mass spectrometer?

A

they hit a negatively charged “detector” plate

37
Q

what occurs when the 1+ ions hit the detector plate?

A

they gain an electron, discharged the ion and producing a current

38
Q

what is the relationship between the current produced and the abundance of ions?

A

the size of the current is proportional to the abundance of those ions hitting the plate

39
Q

how is the data from the detector processed?

A

the detector plate is connected to a computer which produces the mass spectrum

40
Q

formula for velocity

A

(d/t)

41
Q

formula for Ek

A

Ek = 1/2 x m x v^2

42
Q

what are the first 4 subshells

A

s, p, d, f

43
Q

what is elements have an f shell?

A

elements with more than 57 electrons

44
Q

sodium has 11 electrons, what is the electronic configeration

A

1s2, 2s2, 2p6, 3s1

45
Q

what are valence electrons?

A

the electrons located in the outermost electron shell

46
Q

what is ionisation energy?

A

energy required to remove on electron from each atom in 1 mole of gaseous atoms - to form 1 mole of gaseous ions.

47
Q

what are the units of IE

A

kJ mol -1

48
Q

what is the FIRST ionisation energy

A

energy required to remove one electron from one mole of atoms to form one mole of 1+ ions

49
Q

what does the charge of an ion equate to?

A

the level of ionisation energy
eg Cl 4+ = fourth level of ionisation

50
Q

what is the size of the first IE affected by?

A
  • nuclear charge
  • distance from valence electrons to the nucleus
  • shielding
51
Q

what happens to the first ionisation energy across a period?

A

FIRST IONISATION ENERGY INCREASES ACROSS A PERIOD

52
Q

what happens to the first ionisation energy down a group-

A

FIRST IONISATION ENERGY DECREASES DOWN A GROUP

53
Q

why does ionisation energy increase across a period?

A
  • nuclear charge increases
  • therefore, atomic radius of atoms decreases
  • shielding remains quite constant
  • harder to remove an electron so more energy is needed
54
Q

why are there slight decreases in IE1 between beryllium and boron

A

because the 5th electron of boron is in the 2p subshell - which is further away from the nucleus than the 2s subshell of beryllium

55
Q

why is there a slight decrease in IE1 between nitrogen and oxygen

A

due to spin-pair repulsion in the 2Px orbital of oxygen.
in oxygen there are 2 electrons in the 2px orbital, so repulsion between those electrons makes it easier for one of those electrons to be removed

56
Q

why is there a decrease in ionisation energy from one period to the next

A
  • there is increased distance between nucleus and valence electrons
  • increased shielding
57
Q

why does ionisation energy decrease down a group

A
  • number of protons is increased, so nuclear charge increased.
  • distance between nucleus and outer electron increases
  • shielding increases

AQA Chemistry (4 decks)

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