1.2. Mass spectrometer Flashcards
1
Q
What does the mass spectrometer determine?
A
- mass of an isotope/relative mass
- how many isotopes of an element are present in nature (the sample) and their abundance
2
Q
steps in mass spectrometer
A
1) vaporization
2) ionization
3) acceleration
4) deflection
5) detection
3
Q
vaporization
A
- largest possible distance, moving freely
- no interaction between particles; the entirety of E given is used for its purpose - none lost to break bonding
4
Q
ionization
A
- spectrometer not working on non-positively-charged particles
- electron gun is fired - releases huge amounts of E - electrons (1/2) gain energy and jump to higher levels - jump from the last shell (free) - atom becomes positive
- electrons don’t affect mass
- even negatively charged, or non-charged elements become positive
5
Q
acceleration
A
- particles should have equal Ek (when they hit the screen - readings of mass or abundance could be wrong - HUGE systematic error) so they are accelerated using an electric field
- el. field affects only positive particles - reflects them and speeds them up equally
6
Q
deflection
A
- deflected by a magnetic field according to their mass - the smaller the mass, the greater the deflection angle
- also according to their charge - the bigger the charge, the greater the deflection angle
- one magnet=constant magnetic field strength
- diff mass hitting diff. screen areas
7
Q
detection
A
- the beam of ions passing through the machine (screen) is detected electrically
8
Q
to calculate which isotope is more abundant we need to find their…
A
…average, and then compare it with the relative atomic mass (Aˇr) in the PTE - the closer one is more abundant.
9
Q
the percentage abundance of an isotope =
A
detector current for that isotope/the total detector current x 100%
10
Q
relative atomic mass (of the sample)=
A
abundance1mass1+abundance2mass2
