atomic structure Flashcards
what is the tof spectrometer
Detects the mass and relative abundance of isotopes
what are the 3 steps of using a tof mass spectrometer
ionisation, acceleration, detection
two types of ionisation
Electron impact:
Sample vapourised X(g)
Bombarded with electrons from electron gun
X(g)+ e- => X+(g)+ 2e-
Electro spray
Sample dissolved in a volatile solvent
Turned into a fine spay via a charged needle (increases the m/z value by 1)
H+ gained from a solvent
X(g)+ H+ => XH+(g)
what happens during acceleration
Charged plates create an electric field
All ions accelerated forwards with the same kinetic energy (ion drift)
Have diff types velocities due to differences in mass
(More mass=less velocity)
what happens during detection
Negatively charged detector
Positive ions gain electrons at the plate, which cause an electric current
The current is monitored to give a spectra
what is a mass spectra
a graph that shows the relative abundances of the different isotopes (and their masses)
what is symbol for isotopic mass
m/z
(mass: charge ratio)
how to calculate isoptopic mass
find Ar
sum of isotopic mass*percentage
all divideby 100
how to calculate unknown isotopic mass
what else may show up in a mass spectrum?
very small peaks at Mr+1 made up of elemental molecules
i.e 13C and 2H
(only organic molecules)
how to find ratios of different isotopes forming
velocity calculations
(3 formulae need to be used)
KE= 1/2mv2 (rearrange to find v)
convert the grams of the mass of the ion to kg
d=tv (finds length of flight tube)
what are electron orbitals
where electrons are found, within energy levels
order of orbitals (low to high)
s, p, d, f
how many electrons does an orbital hold
2
what is s orbital
spherical in shape, holds up to 2
what is p orbital
figure 8 shape
found in groups of 3 orbitals
what is d orbital
various shapes
found in groups of 5 orbitals
∴ holds up to 10 electrons
what orbitals are in each energy level
Energy level 1: 1s2
Total e:2
Energy level 2: 2s2,2p6
Total e:8
Energy level 3: 3s2,3p6,3d10
Total e:18
Energy level 4: 4s2,4p6,4d10,4f14
Total e: 32
what is hund’s rule
electrons occupy empty orbitals b4 pairing b/c minimises repulsion
∴
what does it means to be isoelectric
means that ions has the same configurstion as some noble gas
exception to orbital energy levels
found in transition metals where 4s is filled in before 3d and electrons lost from 4s before 3d
what is first molar ionisation energy
(making 1+ ions)
The energy required to remove one mole of electrons from 1 mole of the gaseous atoms
X(g) => X+(g) + e-
what is 1st IE dependant on
Nuclear charge more = increase IE
Shielding more = decrease in IE
Distance more = decrease in IE
what are the trends of 1st IE as it goes down a group
decrease
Because nuclear charge increases, however shielding sand distance of the e from the nucleus increases
Which lowers the effective charge on the nucleus
Decreases the attraction between the nucleus and outer e
Lowers the energy required to remove the outer e
what are the trends of 1st IE going across a period
general increase
As nuclear charge increases, there is no change in the amount of shielding/ distance of the outer e from the nucleus
Attraction between the outer e and nucleus increases
more energy need to remove the e
what are the exceptions to trends of 1st IE going across a period
between group 2/3
EG. Be/B
This is because the outer electron in B is in the 2p electron orbitals and the outer e in Be is in 2s orbital
The e in the 2p orbital has the higher e
Therefore is required to remove it
AND between groups 5/6
EG N/O
The outer e in O is paired with another in the 2p orbital
the outer electron in N is not paired
Repulsion between the paired electrons in o means that less energy is required to remove it
This is because e it is easiest remove due to shielding makes a full s orbital
Easier to remove due to repulsion between paired e
what is successive ionisation energy
the energy required to remove es one y one from the same atom
Eg. 2nd ie : X+(g) => X2+(g) + e-
3rd ie: X2+(g) => X3+(g) + e-
what is trend of successive ionisation energies
General increase in ie due to increasing effective charge on the nucleus
describe what is going on in these photos
and how to figure out which group of elements the graph is describing
Large jumps caused by the e being taken from an energy level that’s closer to the nucleus
ie DECREASED distance + DECREASED shielding
Therefore stronger attraction
Pattern in group 1: large jump between successive ie 1+2
group 2: large jump between successive ie 2+3
etc…
