ATOMS Particle Mass Charge Position
Proton 1 +1 nucleus
Neutron 1 0 nucleus
Electron 1/1836 -1 outside nucleus
Filling energy levels
Rules Electrons enter the lowest energy orbital available.
Orbitals can hold a max. of 2 electrons provided they have opposite spin.
Orbitals of the same energy remain singly occupied before pairing up.
This is due to the repulsion between electron pairs.
Order Orbitals are not filled in numerical order (e.g. 4s is filled before 3d) due to
principal energy levels getting closer together further from the nucleus.
ATOMIC STRUCTURE
A T A G L A N C E
KNOCKHARDY
NOTES
A LEVEL CHEMISTRY
ISOTOPES same atomic number (Z) and
different mass number (A)
or same protons and
different neutrons. Na
23
11
Mass number
(protons + neutrons)
Atomic number
(protons)
MASS SPECTROMETER
• Gaseous atoms undergo ionisation by electron bombardment
• Charged particles can be accelerated by an electric field
• Charged particles will be deflected by a magnetic or electric field
The radius of the path depends on mass/charge ratio (m/z)
Heavier ions with larger m/z values are deflected less
If an ion acquires a 2+ charge it will be deflected more.
• Ions detected by electric or photographic methods
Mass spectra can also be used to find relative molecular mass
22
Ne
21
Ne
20
Ne
ANALYSER
ION SOURCE
DETECTOR
ELECTRONIC CONFIGURATIONS
• electrons exist in different energy levels ( n = 1,2,3,4 etc. )
• energy levels can be split into sub levels
• each level contains orbitals (s, p, d, or f)
• each orbital can hold up to 2 electrons
Principal Number of Type of Number of Total number
level (n) sub-levels Orbital Orbitals of Electrons
n = 1 1 1s 1 2 = 2
n = 2 2 2s 1 2
2p 3 6 = 8
n = 3 3 3s 1 2
3p 3 6
3d 5 10 = 18
n = 4 4 4s 1 2
4p 3 6
4d 5 10
4f 7 14 = 32
NOT TO SCALE
INCREASING
ENERGY
4
4s
4p
4d
4f
3
3s
3p
3d
22s
2p
11s
4
4s
4p
4d
4f
3
3s
3p
3d
22s
2p
11s
1s
2s
3s
4s
5s
6s
7s
2p
3p
4p
5p
6p
3d
4d
5d
6d
4f
5f
FILLING
ORDER
© J. L. HOPTON 1997
