Atomic Structure Flashcards
What is time of flight mass spectrometry used for?
-used to measure the relative mass of isotopes
-used in pharmaceutical/forensic/environmental analysis
why is a vacuum required for mass spectrometry?
`so there’s no interference with air particles
ToFMS Stage 1: Ionisation (Electrospray)
- sample is dissolved in a volatile polar solvent and injected through a needle at a high voltage
- Each particle gains a proton and becomes a 1+ ion
ToFMS Stage 1: Ionisation (Electron Impact)
- high energy electrons are fired from an electron gun which knock off an electron each
- This forms 1+ ions
what is the equation for an ion created by electrospray?
X₍₉₎ + H⁺ → XH⁺₍₉₎
what is the equation for an ion created by electron impact?
X₍₉₎ → X⁺₍₉₎ + e⁻
ToFMS Stage 2: Acceleration
-positive ions are accelerated by an electric field to a constant kinetic energy
-velocity depends on mass of the ion
ToFMS Stage 3: Ion Drift
- ions go through a tube of known distance and time that it takes to reach the detector is recorded
- heavier ions take longer to reach detector
- lighter ions reach the detector faster
ToFMS Stage 4: Ion Detection
- positive ions hit a negatively charged plate and pick up an electron each
- this flow of electrons produces a current which is directly proportional to the abundance of the isotopes
ToFMS Stage 5: Data Analysis
- the detector is linked to an amplifier and then to a recorder which converts the current into a peak that is shown in a mass spectrum
- the height of the peak is proportional to the abundance of ion
what equation links the time or mass of an isotope to the time or mass of another
m1/(t1)^2=m2/(t2)^2
How to work out mass of one 1+ particle
m = (mass number ÷ Avogadro’s Constant)/1000
how would you find the Mr of a sample from the m/z values (TOF mass spectrometry) when doing electron impact ionisation
the Mr is equal to the peak with the greatest m/z value
how would you find the Mr of a sample from the m/z values (TOF mass spectrometry) when doing electrospray ionisation
the Mr is equal to the peak with the greatest m/z value minus one
what is the definition of relative atomic mass
The average mass of an atom of an element, relative to 1/12th of the mass of an atom of carbon-12
how would you calculate relative atomic mass
sum of (isotope abundance x isotope number) / sum of isotope abundance
what is the order of increasing energy of the energy sublevels
s→p→d→f
how many orbitals does each sublevel (s,p,d,f) have
s - 1 orbital
p - 3 orbitals
d - 5 orbitals
f - 7 orbitals
how many electrons does each sublevel (s,p,d,f) hold
s - 2 electrons
p - 6 electrons
d - 10 electrons
f - 14 electrons
what is the order in which energy levels are filled
1s, 2s, 2p, 3s, 3p, 4s, 3d, 4p, 5s ….
why are electrons removed from energy level 4s before 3d
4s is lower in energy than 3d
what are the exceptions to the standard electronic configuration
chromium
- 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d⁵
- more stable as a half subshell (3d⁵)
Copper
- 1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹, 3d¹⁰
- more stable as a full subshell (3d¹⁰)
