Atomic Structure Flashcards
What does a Mass Spectrometer measure?
The relative mass of isotopes
What are the stages a Time of Flight mass spectrometer?
• ionisation
• acceleration
• ion drift (distance)
• detection
• analysis
Outline Electrospray Ionisation
- sample dissolved in polar solvent
- injected through a needle at a high voltage
- each particle gains a proton (H+) to form 1+ ions
What is the equation for electrospray?
X(g) + H+ > XH+(g)
What is electron impact?
• high energy electrons fired from electron gun
• knocks of an electron from each particle
• form 1+ ion
What is the equation for Electron impact?
X(g) > X(g) + e-
What happenes during Acceleration in TOF?
• positive ions are accelerated by an electric field to a constant KE
( velocity depends in mass of ion)
Ions with lower mass travel faster
What happens during Ion Drift in TOF?
• ions separate
• they drift in a flight tube of know distance and time taken is recorded
• TOF depends on velocity
What happens during ion detection in TOF?
• positive ions hot detector and pick up an electron
• causes a current to flow
( more ions hitting detector bigger current)
Why is a vaccum required in TOF
So no other particles can be detected and interfere
Equation for mass(kg) of each 1+ particle
( Mass number/Avagadro ) / 1000
Equation to find Velocity with KE and mass
v = √2KE / m
What equation can you use if you’re not given distance?
m1 m2
—- = —-
(t1)2 (t2)2
What is the formula for relative atomic mass
average mass of an atom of an element
——————————————————-
1/12 mass if an atom an atom of 12C
Equation to calculate relative atomic mass from peaks
sum (m/z of a peak x abundance of that peak)
————————————————————
sum of abundances