dr mckenzie - atomic structure

Question 1

what is the first stage of time of flight spectrometry?

Answer 1

ionisation

Question 2

what are the two ways of ionisation?

Answer 2

electron impact and electrospray ionisation

Question 3

when is electron impact used?

Answer 3

for elements and low mr compounds

Question 4

when is electrospray ionisation used?

Answer 4

used for high mr compounds

Question 5

what happens in electron impact?

Answer 5

high energy electrons are fired at the sample from an electron gun, it knocks off an electron from each atom to form a +1 ion

Question 6

what is the first step in electrospray ionisation?

Answer 6

sample is dissolved in a volatile solution and injected through a fine hypodermic needle as a spray into a vacuum in ionisation chamber

Question 7

what is the second step in electrospray ionisation?

Answer 7

particles gain a proton and become ions as a mist then the solvent evaporates leaving +1 ions

Question 8

what is applied to the end of the needle in electrospray ionisation?

Answer 8

very high voltage

Question 9

is the needle positively or negatively charged in electrospray ionisation?

Answer 9

positively

Question 10

what is the second stage of tof?

Answer 10

acceleration of ions

Question 11

what happens during acceleration of ions?

Answer 11

ions are accelerated using an electric field

Question 12

why do ions need to be accelerated in tof?

Answer 12

so all ions have the same kinetic energy

Question 13

what is the third stage of tof?

Answer 13

separation of charged ions

Question 14

what is the first step of separation of charged ions called?

Answer 14

ion drift

Question 15

what happens during ion drift?

Answer 15

ions then enter the flight tube

Question 16

what is the relationship of ion drift with mass?

Answer 16

ions with different masses have a different time of flight

Question 17

what happens if ions are lighter in ion drift?

Answer 17

lighter ions travel faster and take less time to reach the detector

Question 18

what is the fourth stage of tof?

Answer 18

detection

Question 19

what is the first step of detection?

Answer 19

currents are produced when ions hit the negatively charged plate

Question 20

what is the second step of detection?

Answer 20

mass spectrum shows the number of particles of each mass that hit the detector

Question 21

what is number of particles also referred to as?

Answer 21

abundance

Question 22

how can you determine the mass of the ions hitting the detector?

Answer 22

it can be calculated via the time of flight

Question 23

why could a current be bigger during detection?

Answer 23

this means more ions hit the detector

Question 24

what is the x axis on a tof graph?

Answer 24

m/z - mass to charge ratio , NOT mass

Question 25

in an electrospray ionisation mass spectrum what would be the mr if the peak was 505?

Answer 25

504 because the main peak tends to be mr +1 so mr is 1 less than molecular ion peak

Question 26

how do you work out the average mass of atoms?

Answer 26

total mass of all the atoms / total number of atoms

Question 27

in organic molecules, why is there often a small peak at the mr +1?

Answer 27

there can be a small number of molecules containing 13^C or 2^H atoms

Question 28

when do peaks tend to be more significant in tof?

Answer 28

when there are molecules that contain atoms with significant amounts of isotopes

Question 29

how to find out ke?

Answer 29

1/2 mv^2

Question 30

how to find velocity?

Answer 30

2ke / m

Question 31

what is t in tof?

Answer 31

time of flight

Question 32

what is time of flight unit

Answer 32

seconds

Question 33

what is d in tof?

Answer 33

length of flight tube

Question 34

what is length of flight tube unit?

Answer 34

metres

Question 35

what is v in tof?

Answer 35

velocity of particle

Question 36

what is velocity of particle unit?

Answer 36

m/s

Question 37

what is m in tof?

Answer 37

mass of particle

Question 38

what is mass of particle unit?

Answer 38

kg

Question 39

what is ke in tof?

Answer 39

kinetic energy of particle

Question 40

how do you work out the mass of one particle?

Answer 40

mass/1000 / 6.022 x 10^23

Question 41

how to work out distance in tof

Answer 41

Question 42

how to work out time in tof

Answer 42

Question 43

how to work out mass in tof

Answer 43

Question 44

how many electrons does the s orbital hold?

Answer 44

2

Question 45

how many electrons does the p orbital hold?

Answer 45

6

Question 46

how many electrons does the d orbital hold?

Answer 46

10

Question 47

how many electrons does the f orbital hold?

Answer 47

14

Question 48

what are the two anomalies when it comes to electron config?

Answer 48

copper and chromium

Question 49

why are copper and chromium anomalies?

Answer 49

instead of losing an electron in the d orbital, they lose it in 4s

Question 50

why is there a dip from group 2 to 3?

Answer 50

it changes from the s to p orbital

Question 51

why is there a dip from group 5 to 6?

Answer 51

extra electrons cause repulsion as it is 4s

Question 52

what is the term first ionisation energy?

Answer 52

the energy required to remove an electron from each of a mole free gaseous atom of that element