Atomic structure Flashcards
mass of an electron
1/1840
isotopes definition
same protons
different number of neutrons
what are the 4 steps in mass spectrometry
1.ionisation
2.acceleration
3.flight tube
4.detection
two types of ionisation
electron impact- used for elements with low formula mass /causes fragments to larger molecules
electrospray ionisation- used for larger molecules/fragmentation does not occur
Electron impact process
-vaporized sample is injected at low pressure
-electron gun fires high energy electrons at sample
-knocks out an outer electron
-forming positive ions with different charges
Electrospray ionisation process
-sample is dissolved in a volatile solvent
-injected through a fine needle giving a fine mist
-tip of the needle has high voltage
-at the tip sample gains a proton
acceleration process
-positive ions are accelerated by an electric field
-to a constant kinetic energy
flight tube process
-heavier particles take longer to move through the drift area
-ions are distinguished by different flight times
detection process
-ions reach the detector and generate a small current which is fed to a computer for analysis
-current is produced by addition of e- to the positive ions
-size of the current is proportional to the abundance of species
2 equations to use to calculate time of flight
t=d/v
v=square root ((2KE)/m)
m=mass in kg
v=velocity in m/s
distance=m
relative atomic mass definition
the ratio of the average mass of one atom of an element relative to one twelfth of the mass of an atom of carbon-12.
relative atomic mass equation
=sum of (isotopic mass x %abundance)/100
order of orbital subshells
s p d f
rule between 4s and 3d electrons
When forming ions e- are lost in 4s before 3d
define first ionisation energy
the enthalpy change when one mole of gaseous atoms forms one mole of gaseous ions with a single positive charge
