3.11 - Atomic Structure Flashcards
What are the two types of ionisation and why is it needed
- electrospray
- electron impact
to accelerate and to deflect the beam
What is electron spray?
- sample is dissolved in a solvent
- and injected through a needle at high voltage
- each particle gains a proton
X + H+ —> XH+
What is electron impact?
- the sample is bombarded by high energy electrons
- the sample electron loses an electron forming M+
Define first ionisation energy
The energy required to remove one electron from each atom in a mole of gaseous atoms producing one mole of 1+ gaseous ions
What 3 factors affect ionisation energy?
- nuclear charge increases I.E increases bc there’s more protons so stronger attraction for electrons
- distance from nucleus increases I.E decreases
- shielding increases I.E decreases bc less energy required to remove outer electron
What is the general ionisation energy trend across periods?
- Ionisation energy increases
- because nuclear charge increases and shielding stays roughly the same
- outer electrons are more attracted to the nucleus
Why does the ionisation energy decrease from group 2 to 3?
P orbital is higher energy than S orbital - So easier to lose electron
Why does the ionisation energy decrease from group 5 to 6?
Extra electron to electron repulsion make it easier to lose electron
KE = ?
1/2mv^2
v = ?
Square root: 2KE/m
Time of flight (with velocity) =
Length of Flight tube x square root: m/2KE
number of moles =
Number of particles / avagadros constant
grams to kg = ?
divide by 1000
mass of atom (kg)?
mass number/ avagadros constant , then divide that by 1000 to get it in kg
What is shielding?
The number of inner electrons - the more inner electrons, the more shielding
what’s the electron configuration of Cu?
1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d10
what’s the electron configuration of Cr?
1s2, 2s2, 2p6, 3s2, 3p6, 4s1, 3d5
What are the different stages of mass spectrometry in order?
1) ionisation (2 types)
2) acceleration
3) flight tube
4) detection
Explain how ions are accelerated detected, and have their abundance determined in a spectrometer
- ions accelerated by attraction to negatively charged plate.
- ions detected by gaining electrons
- Abundance, determined by size of current flowing in the detector
Define relative atomic mass
Average mass of all isotopes of an element compared to 1/12 the mass of an atom of carbon 12
Define relative molecular mass
The weighted average mass of 1 molecule compared to 1/12 the mass of an atom of carbon 12
What’s the trend in ionisation energy down a group
- ionisation energy decreases
- atomic radius and shielding increases
- so outer electrons further from the nucleus
- so weaker attraction towards the nucleus
What’s the equation for second ionisation energy
X+(g) —> X2+(g) + e-
What’s the equation for first ionisation energy
X (g) —> X+(g) + e-
what is the evidence for shells?
there is a sharp drop in ionisation energy between the end of 1 period and the start of the next
How do you get from cm to m
Divide by 100
How do you work out number of neutrons
Mass number - atomic number
How is relative abundance measured in a TOF mass spectrometer
Current is proportional to abundance
Define 2nd ionisation energy
The enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous ions with a double positive charge
What is successive ionisation
The removal of more than 1 electron from the same atom
What does it mean if you’re asked to find “ONE MOLE of X” in g
Find the Mr
What is not deflected by an electric field
A neutron
Why is an element in the p/d block of the periodic table
Because it’s outer electron is in the 3p/3d sub shell
