Atoms, ions and compounds Flashcards
Aufbau principle
electrons enter lowest energy orbital available
Hund’s rule
electrons prefer to occupy orbitals in their own and only pair up when no empty shells are availible
number of orbitals in sublevel s
1
number of orbitals in sublevel p
3
number of orbitals in sublevel d
5
number of orbitals in sublevel f
7
ionisation energy
energy required to remove an electron from its shell
Order electrons fill up shells
1s 2s 2p 3s 3p 4s 3d 4p
Isoelectronic
Species with the same electronic configuration
1st ionisation energy
Energy required to remove one electron from each atom in a mole of gaseous atoms producing 1 mole of 1+ gaseous ions
2nd ionisation energy
The energy require to remove the 2nd electron from each atom in a mole of gaseous atoms (starting with the 1+ ion)
3 Factors affecting ionisation energy
- distance from nucleus (atomic radius)
- nuclear charge
- shielding
as you go down a group, 1st ionisation energy…. because….
- decreases
- greater atomic radius, more shedding and less attraction between nucleus and electron
as you go across a period, 1st ionisation energy…. because….
- increases
- more protons, same shielding, smaller atomic radius
2 dips in the ionisation trend (period)
group 2 to 3 (Mg, Al)
group 5 to 6 (P, S)
What causes the dip in the trend between Mg and Al
Al has a higher energy electron (3p) which is slightly further out so if lost more easily
What causes the dip in the trend between P and S
P has 1 electron in outer shell, S has 2 which repel each other and so lost more easily
degenerate orbitals
those with exactly the same energy
principle quantum number
shall number
shape of s-orbital
spherical - 2 electrons can be anywhere within the sphere
shape of p orbitals
dumbell shaped - move anywhere within the shell
4 stages of mass spectrometry
ionisation
acceleration
ion drift
detection
2 main techniques of ionisation
electrospray ionisation
electron impact ionisation
process of electrospray ionisation
- sample dissolved in solvent
- high voltage is applied
- voltage rips an electron off the solvent and attached it to the sample molecules
- creating positively charged ions
main advantage of electrospray ionisation
doesn’t cause fragmentation
typical uses of electrospray ionisation
polymers or biological materials - ie. DNA
process of electron impact ionisation
- sample is vaporised
- and then hit with electrons from an electron gun
- electrons knock electrons from molecules
- forming positively charged ions
process of acceleration of the sample
- molecules are accelerated to the same kinetic energy
- speed as different depending on the mass of the molecule
- lighter particles have a greater velocity and so hit the detector plate first
- lighter particles detected before heavier particles
process of ion drift
- time of flight = distance/velocity
- ∴ time = distance x √ m / zKE
- lighter ions take less time as time is dependant on √ m
process of detection
- ions hit negatively charged plate
- causes a current, size of current gives a measure if the number of molecules hitting the plate
- gives an abundance of the molecule
x-axis of the spectrum
mass/charge ratio
y-axis of spectrum
% abundance
molecular ion peak
peak of greatest mass/charge ratio
smaller peaks in spectrum are due to
isotopes of different masses ∴ different mass/charge ratios
smaller, significantly lighter peaks due to
fragmentation of the molecule
e. to find RAM of a substance using mass spectrometry
(isotope abundance % x isotope mass )/100
2 exceptions of patter of loss of electrons from 4s before 3d
Cr - 4s1 3d5 - energetically favourable to have both half filled
Cu - 4s1 3d10 - energetically favourable to have 3d fully filled
orbital
a region around the nucleus that can hold up to 2 electrons
how do you determine the mass of an isotope
using a mass spectrometer
how does a mass spectrometer work?
- sample vaporised
- then ionised to form positive ions
- ions accelerated - heavier = slower + more difficult to deflect
- ions detected on mass spectrum as a mass-to-charge
- ratio is equivalent to relative isotopic mass
how calculate mass-to-charge ratio?
mass of ion/charge of ion
polyatomic ion
ion formed of atoms of more then 1 element bonded together
binary component
- eg.
2 elements only
- sodium oxide
