atomic structure

Question 1

time of flight mass spectrometry is…

Answer 1

an instrument used to measure the relative mass of isotopes

Question 2

environmental use of TOF

Answer 2

drinking water testing,
pollution screening

Question 3

clinical use of TOF

Answer 3

drug discovery studies,
pre-clinical studies

Question 4

forensic use of TOF

Answer 4

trace evidence,
arson investigation

Question 5

5 steps to TOF

Answer 5

1. ionisation
2. acceleration
3. ion drift
4. ion detection
5. data analysis

Question 6

2 types of ionisation…

Answer 6

electrospray ionisation,
electron impact ionisation

Question 7

elecrospray ionisation

Answer 7

sample is dissolved in a volatile polar solvent,
injected through a needle at a high voltage,
X (g) + H+ → XH+ (g)

Question 8

electron impact ionisation

Answer 8

high energy electrons are fired from an electron gun,
to knock off an electron from each particle
X (g) → X+ (g) + e-

Question 9

acceleration

Answer 9

positive ions accelerate through a negative electric field at constant kinetic energy
KE = 1/2 × m × v²
velocity depends on the mass of the ion

Question 10

ion drift

Answer 10

v = d/t
ions with a lower mass have a higher velocity, therefore reach the detector first.
ions with a higher mass have a lower velocity, therefore reach the detector last.

Question 11

ion detection

Answer 11

positive ions will reach the detector first and pick up an electron which causes a current to flow
current is directly proportional to abundance

Question 12

data analysis

Answer 12

the detector is linked to an amplifier, linked to a recorder which shows the mass spectrum.
height of peak is proportional to the abundance
abundance v mass/ charge ratio

Question 13

why is a vacuum required

Answer 13

so no other particles interfere with the results

Question 14

what happens when 2 electrons are knocked off during ionisation

Answer 14

the m/z value halves, so the mass of the particle is half

Question 15

mass in kg of a 1+ particle=

Answer 15

mass number ÷ 6.022×10²³ ÷ 1000

Question 16

kinetic energy=
(units)

Answer 16

KE= 1/2 × m × v²
J kg ms‐¹

Question 17

velocity=
(units)

Answer 17

v = d ÷ t
ms‐1 m s

Question 18

simplified equation for questions in terms of mass and time

Answer 18

m¹ ÷ (t¹)² = m² ÷ (t²)²

Question 19

relative atomic mass equations

Answer 19

• average mass of one atom of an element compared to 1/12 mass of an atom of carbon-12

Question 20

in electron impact, the mr of the sample is…

Answer 20

equal to the peak with the greatest m/z value

Question 21

in electrospray, the mr of the sample is…

Answer 21

equal to the peak of greatest m/z value minus 1

Question 22

how many peaks does 1 chlorine have, to what ratio

Answer 22

2 peaks, 3:1

Question 23

how many peaks does 2 chlorine have, to what ratio

Answer 23

3 peaks, 9:6:1

Question 24

how many peaks does 1 bromine have, to what ratio

Answer 24

2 peaks, 1:1

Question 25

how many peaks does 2 bromine have, to what ratio

Answer 25

3 peaks, 1:2:1

Question 26

regular electron configuration

Answer 26

1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p⁶ 5s² where electrons are removed from the level of highest number

Question 27

electron configuration for [Cr]

Answer 27

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d⁵ - so the outer shell is half full and more stable - electrons are still removed from 4s group first

Question 28

electron configuration for [Cu]

Answer 28

1s² 2s² 2p⁶ 3s² 3p⁶ 4s¹ 3d¹⁰ -so the outer shell is more stable as it is full - electron still removes from 4s first

Question 29

First ionisation energy

Answer 29

the minimum amount of energy required to remove an electron from a gaseous atom to form a gaseous 1+ ion

Question 30

1st IE trend down a group:

Answer 30

IE decreases number of shells increases, shielding increases weaker electrostatic attraction between positive nucleus and negative outer electron less energy required to remove an electron

Question 31

1st IE trend across a group:

Answer 31

IE increases same number of shells, similar shielding increase in protons stronger attraction between positive nucleus and negative outer electrons more energy required to remove

Question 32

group 3 1st IE deviation

Answer 32

IE decreases electron is removed from a higher p sub-level less energy is required to remove the electron

Question 33

group 6 1st IE deviation

Answer 33

IE decreases pair of electrons in the p orbital an extra repulsion means less energy is required to remove an electron

Question 34

successive ionisation energy

Answer 34

increases more difficult to remove an electron from a more positive ion ionic radius decreases attraction between nucleus and outer electron increases

Question 35

John Dalton

Answer 35

1803 all matter was made of the same tiny sphere particles called atoms

Question 36

JJ Thompson

Answer 36

1897 'plum pudding' model discovers electrons atoms are a sphere of positive charge with negative electrons dotted around inside

Question 37

Rutherford

Answer 37

1909 positively charged particles are fired at very thin gold foil, and many pass through should not have worked according to 'plum pudding' model therefore: atoms have a centeral positively charged nucleus electrons orbit the nucleus

Question 38

Niels Bohr

Answer 38

1913 electrons occupy energy levels around the nucleus

Question 39

James Chadwick

Answer 39

1932 there are neutrons in the nucleus of the atom

Question 40

cation

Answer 40

positive ions where there is less electrons than protons

Question 41

anion

Answer 41

negative ion where there is more electrons that protons