3.1.1 atomic structure Flashcards
history of the atom
lol
what happens when an e- gains/loses energy
when an e- gains energy it gets excited and moves to a higher energy level. when it loses energy it relaxes to its ground state
anion
-ve ion
cation
+ve ion
isotope
atom of an element with the same number of protons and a different number of neutrons
(you can have ions of isotopes)
why do isotopes of they same element have the same chemical properties
because they have the same electron configuration/ number of e-
why do isotopes of the same element have different physical properties
bc they each have a different number of neutrons.
isotopes with more neutrons have
1. higher mass
2. higher density
3. higher m/b points
4. slower diffusion rates
relative atomic mass
how is it calculated
average mass of an atom of an element to 1/12 the mass of a C12 atom
using abundance of isotopes
what is an energy level
specific orbits which electrons occupy as they orbit around the nucleus
each energy level represents a specific energy value
each energy level contains a different number of electrons
as you go further out energy values are higher
what is a sublevel
energy levels can be broken down into sublevels: s, p, d etc.
energy level one only has s
el 2 has s and p
el 3 has s, p, d
what is an orbital
sublevels can be broken down into orbitals. these are basically areas where electrons probably occupy. there are max 2 electrons in each orbital
the s sublevel has 1 orbital, so 2 e-
the p sublevel has 3 orbitals; 6
the d sublevel has 5 orbitals; 10
why does 4s fill before 3d
as we go further out from the nucleus the sublevels overlap more and more. 4s is actually of lower energy than 3d. according do Aufbau principle, electrons fill the lowest energy orbitals. once it fills it’s of higher energy.
the diagonal rule can be used to identify which sublevels come next
two types of representing electron configuration
standard
and short structure, where you use the nearest noble gas in square brackets then add the extra e-
what are two special cases of e- configuration
chromium
copper
special case of chromium
should be the standard configuration but instead it ends in
4s13d5
because electron is demoted from 4s to 3d because atoms are more stable with a half set of orbitals
special case of copper
should be the standard configuration but instead it ends in
4s13d10
because electron is demoted from 4s to 3d as the atom is more stable with a full set of 3d orbitals
ionisation energy
energy required to remove one mole of electrons from one mole of atoms in gaseous state
units of IE
KJmol^-1
why is the reaction of IE endothermic
energy needs to be taken in by the outer e- being removed to overcome the eFoA between the nucleus and itself
def 2nd IE
energy required to remove one mole of electrons from +1 ions (!!) in a gaseous state
how can we quickly form the IE equation for different IEs?
nth IE ;
then the product of the reaction is +n charge
why is 1st IE the lowest value always
eFoA is stronger in +ve ions compared to a less positive or neutral atom because there is more positive acting on the outer e-
each time requires more energy; you’re trying to remove from an increasingly +ve ion
what are successive ionisation energies
they are the IEs (in KJmol^-1) to remove successive electrons from the same atom
results can be logged on a graph and conclusions have been made for it
what can be observed from a graph depicting successive IEs?
- different electrons require different amounts of energy to be removed
- graph is not linear
- jumps in the graph (indicate energy levels)
how do jumps in the successive IE graph show existence of energy levels
what do the gradual increase lines mean
in a jump from X to y, the y electron must be significantly closer to the nucleus bc there is a significant amount of energy it needs more than X electron.
expected bc ion is increasingly+ve
how can you tell group number from successive IE data
how can you tell period number
identify big jumps in the numbers
group number = e- in outer energy level
however many electrons before 1st jump = group number
period number is no. energy levels.
n+1 rule: no. energy levels is the no. jumps add 1
what happens to IE value down a group
it decreases
what factors affect the strength of the eFoA between the nucleus and outer e-
nuclear charge
distance between the nucleus and outer e-; atomic radius
shielding
why does IE decrease down a group
nuclear charge increases but this is offset by the
1. increase in atomic radius due to more completed energy levels making the electron further away from the nucleus therefore decreased FoA
- increase in shielding because there are more completed energy levels which weakens the FoA
what does the trend of group IE decreasing show
probes that the outer e- as you go down must be further away and with more shielding
we would expect it to be greater and greater due to the increased nuclear charge. so the fact it decreases indicates the presence of energy levels, causing this effect of atomic radius and shielding
what is the trend in IE across a period
it increases overall
what is the reason for the trend in IEs across a period
there is a negligible increase in shielding because sublevels are being filled
there is an increase in nuclear charge so the eFoA increases, making the overcoming of that require more energy
there is a DECREASE in atomic radius because nuclei are better at attracting e-s (more protons). so increased FoA; the e- cloud is slightly closer.
where are the deviations from the overall trend in IE across a period
why?
groups 2 -> 3
outer e- is being removed from an orbital of higher energy (be specific in questions) so less energy is needed to remove it.
groups 5 -> 6
there is a pairing of e-s in the orbital of gr6 atoms where there isn’t in gr5. so electron repulsion. less energy needed to remove it
what does this give evidence for ?
the deviations can be explained by the existence of energy levels, sublevels and orbitals
how to compare IEs
make sure know the e- configuration for whatever is brings asked, atom or ion
who has a smaller atomic radius?
who has more shielding?
which orbital is outer e-?
who has higher nuclear charge?
which main energy level?
what is TOF mass spectrometry
? Girl beats me
what’s the abbreviated process
VIA DD
vaporisation
ionisation
acceleration
drift
detection
in vaporisation…
substance is made into a gas bc . needs to
in ionisation…
the particles are made to have +ve charges because that is the only way they can be accelerated and detected.
they can have this done in two ways:
electron impact
or electrospray
electron impact
high energy electrons are fired from an electron gun at the sample. knocks off an electron and results in a +1 charge
this is usually done for
electrospray
dissolve sample in polar volatile solvent;
inject through a fine hypodermic needle to give a fine mist;
top of needle has a high voltage;
gains a proton as it leaves the needle
charged sample moves toward -ve plate and repel as they get closer so a stream of charged particles is produced
in acceleration…
ions are accelerates using an electric field so ions all have the same kinetic energy. they are headed towards a -vely charged plate.
heavier ions will have slower velocity, therefore hit the detector plate later. so different mass ions have different times of flight
in drift…
ions passing through the flight tube (vacuum so doesn’t hit air particles) towards detector.
time of flight determines the mass of the ion (have the KE, the distance and now the time)
equation for determining mass of ion with tof ms
t= d√(m/2ke)
time, s
distance (of flight tube), m
mass, kg
ke, J
in detection…
electron transfers from the detector to the +be ion when the ion hits it. this induced a current. the size of this current tells us the abundance of that ion because they will all hit at same time (same mass so same tof)
how many different currents you get (or at different times idk?) tells you the number of isotopes. the size for the current is proportional to abundance of that isotope.
if electrospray is used, when reading a m/z graph we need to
take away 1 from mass reading because a proton has been added
reasonably sized peaks on an m/z graph indicate
an isotope
m/z graphs shows the
relative abundance (obtained from current) of different isotopes of an element sample
m+1 peaks
for molecules, small peaks to the right of the main peak showing molecular mass are due to there being different isotopes of elements used in the molecules eg C13 instead of C12 and H2 instead of H1
the Mr of a compound from a graph
the leak with the greatest (!) m/z value ignoring m+1 peaks. this is the molecular ion peak
