DN1). Atomic Structure Flashcards
Neutron
Rel charge, rel size, actual charge(C), actual size(kg)
0 , 1 , 0 , 1.675x10^-27
Electron
Rel charge, rel size, actual charge(C), actual size(kg)
-1 , 1/1836 , 1.602x10^-19 , 9.109x10^-31
Mass number
Protons + neutrons
Proton number
Number of protons or electrons
Atoms are….
Neutral
Equal number of protons and electrons
Ions are formed by….
Adding or removing electrons
Negative if adding, positive if removing
Isotopes are
Atoms with the same number of protons as each other but different number of neutrons
Physical properties of isotopes are…
Different
Chemical properties of isotopes are…
The same (electrons)
How to calculate RFM:
Total amount
Relative atomic mass (Ar)
Weighted average mass of an atom of an element taking into account all the naturally occurring isotopes relative to 1/12 the relative atomic mass of an atom of carbon 12
Use of the time of flight mass spectrometer
Gives accurate information about RFM and isotopic abundance
Helps to identify elements and molecules
4 simple steps of a time of flight mass spectrometer
Electrospray ionisation
Acceleration
Ion drift
Detection
Electrospray ionisation
Beam of electrons fired at sample –> ionises sample by knocking out an electron
M(g) + e- ———> M+(g) + 2e- (Should happen)
M(g) + e- ———> M2+(g) + 3e- (can happen if electron too energetic)
Why is Electrospray ionisation used
Because it reduces the number of molecules that fragment
Acceleration
An electric field (negative) attracts the positive ions
The ions accelerate towards it
Some are discharged (if they hit the plate) but some escape through a hole in the plate = beam of positive ions
Ions with the same charge have the same kinetic energy and are travelling at the same speed
Ion drift
Ions entering have two variables (charge, z & mass, m)
Time taken = m/z mass charge ratio
Bigger number = longer time of flight
Detection
Time of flight detected by computer
Positive ions hits metal plate and pulls off an electron
This generates an electric current
More ions = bigger current , measured by detector
Br abundance
50% Br-79, 50% Br-81
Cl abundance
75% Cl-35, 25% Cl-37
Why are there often small peaks at m/z +1
Because of H-2 and C-13
Explain chlorine TOF
(Cl-35—Cl-35)+ 3/4 x 3/4 = 9/16
(Cl-37—Cl-35)+ 3/4 x 1/4 = 3/16 X2 as two ways round
(Cl-37—Cl-37)+ 1/4 x 1/4 = 1/16
So three peaks each separated by two units in the ration 9:6:1
RFM=
m/z
Relative atomic mass formula=
Abundance
Relative formula mass from TOF
m/z
Sub level s
Number of orbitals 1
Maximum number of electrons 2
Shape Spherical
Sub level p
Number of orbitals 3
Maximum number of electrons 6
Shape py, px & pz
Sub level d
Number of orbitals 5
Maximum number of electrons 10
Shape -
Sub level f
Number of orbitals 7
Maximum number of electrons 14
Shape -
The sequence orbitals fill up
1s 2s 2p 3s 3p 4s 3d
4s sub-shell
Fills before 3d
Empties before 3d
Special two which don’t fill as u would expect
Chromium (4s1 3d5 as more stable)
Copper (4s1 3d10 as more stable)
Ionisation energy
This involves taking away the outer electron from an atom or ion
First ionisation energy
The enthalpy change for removing one more of electrons from one mole of their atoms in gaseous state
3 factors that influence ionisation energy
Nuclear charge
Distance of outer electron from nucleus
Shielding
Down a group ionisation energy……
Decreases
Ionisation energy across a period…
Increases
Special phrase
Which is higher in energy therefore electron is easier to remove
Proton
Rel charge, rel size, actual charge(C), actual size(kg)
+1 , 1 , 1.602x10^-19 , 1.673x10^-27
first ionisation equation
X(g) —–> X(g)^+ + e^-
second ionisation equation
X^+ ——> X^2+ + e^- (all with state symbol g)
