Atomic Structure

Question 1

what does a mass spectrometer do?

Answer 1

it detects the mass and relative abundance of isotopes

Question 2

what are the 4 steps in TOF mass spectrometry?

Answer 2

1. Ionisation
2. Acceleration
3. flight tube/Ion drift
4. Detection

Question 3

what are the 2 types of ionisation in TOF mass spectrometry?

Answer 3

1. Electron impact
2. Electrospray ionisation

Question 4

what happens during electrospray ionisation?

Answer 4

. the sample is dissolved in a volatile solvent
. this is then turned into a fine spray via a charged needle
. a H+ ion is gained from the solvent.

IMPORTANT: this increases the m/z by 1

Question 5

what happens during electron impact?

Answer 5

. the sample is heated (vapourised)
. the sample is then bombarded with electrons from an electron gun
. this causes an electron to get knocked off the sample forming a positive charged sample

Question 6

what happens during the process of acceleration in the TOF mass spectrometer?

Answer 6

. the charged plates create an electric field
. all ions are accelerated to the same kinetic energy, however, they have different velocities due to differences in mass

Question 7

what happens during the flight tube/ion drift in TOF mass spectrometry?

Answer 7

. isotopes are separated from each other due to their differences in mass, causing them to move down the flight tube at different speeds
. lighter ions move faster
. heavier ions move slower

Question 8

what happens during the process of detection in TOF mass spectrometer?

Answer 8

. negatively charged detector
. positive ions gain electrons at the negative plate, which causes an electrical current
. this current is then monitored and analysed to form a mass spectra

Question 9

what is an isotope?

Answer 9

atoms of the same element that have the same number of protons and electrons, however they have a varied number of neutrons.