the structure of atoms Flashcards
what is the mass of a proton?
1
the charge of a proton?
+1
what is the mass of a neutron?
1
what is the charge of a neutron ?
0
what is the mass of an electron ?
negligible
what is the charge of an electron ?
-1
what is meant by the relative atomic mass (Ar) ?
the mass of an atom relative to the 12C isotope with value of 12
what is the calculation for Ar
average mass per atom of an element / mass of one atom of Carbon-12 x12
what is meant by mass spectroscopy ?
mass spectroscopy is an instrumental technique used to find the relative mass of elements and compounds
what occurs in electrospray ionisation ?
- the element is dissolved in a volatile solvent.
- the dissolved solvent is then forced into a very thin needle and is then sprayed
- the end of the needle is then put through a very high voltage which forces the solvent to gain a H+ proton which therefore makes it become a positive ion
what is meant by a volatile solvent ?
a volatile solvent makes the element turn into a gas very easily
what happens during the electric field in the time of flight spectrometer ?
- the ions are all accelerated by an electric field so that all of the ions have the same kinetic energy at a specific point
-its calculated using : kinetic energy = 0.5 x mass x velocity ^2
what happens in the flight tube in the ToF mass spectrometer ?
-the ions enter the flight tube
- because the ions have different isotopes, they all have different masses and times of flight
- lighter ions = shorter time of flight
heavier ions = longer time of flight
what is the term used when ions enter the flight tube ?
ion drift
what is the detector ?
a negatively charged plate
what happens when the ions hit the plate ?
when ions hit the plate a current is produced
- so the more ions that hit the detector the bigger the current
how are we able to calculate the abundance (number of particles ) of the particles ?
because the size of the current is directly proportional to the number of ions hitting the plate
how can we calculate the mass of ions hitting the detector ?
from the time it takes to reach the detector
what is the equation for electrospray ionisation ?
element X (g) + H+ —> XH+ (g)
electron gun ionisation method ?
- element sample is vapourised into a gas
- it passes through the machine and an electron gun bombards high energy electrons at the sample
- this forces the element to lose an electron as it knocks it off
therefore forming a +1 ion
what is the equation for electron gun ionisation ?
element X(g) —-> X+ (g) positive ion + e-
- as it loses an electron
relative atomic mass of isotopes equation ?
Ar = total mass of all isotopes / total abundance
