Atomic Structure Flashcards
Isotopes
Atoms of same element that have same number of protons but different number of neutrons
Same chemical properties but different physical properties
Relative abundance
(Abundance x Mass) + (Abunda…)
What do chemical and physical properties depend on
Chemical: Electronic configuration
Physical: Number of neutrons so different mass
Electron impact ionisation conditions and Electron spray
• Impact: Lower molecular mass, has fragments
• Spray: Higher molecular mass, fragmentation unlikely
Fragmentation- ion that’s broken down
Electron Impact Ionisation
• Vapourised
• Bombarded with high energy e- fired from e- gun
~ emits e as current runs through it
• e knocked off particle to form 1+ ion
• Attracted to negatively charged plate
• Accelerated through mass spectrometer
• Ion could be fragmented, causes peaks on mass spectrum
• X(g) —> X^+(g) + e-
Electron Spray Ionisations
• Sample dissolved in volatile solvent
• Solvent injected in mass spectrometer with hypodermic needle which produced fine mist
• Needle attached to high voltage power supply
• Particles ionised by gaining proton form solvent
• Solvent evaporates and XH^+ attracted to negatively charged plate
• Accelerated through mass spectrometer
• X(g) + H^+ —> XH^+(g)
Acceleration of TOF MS
• 1+ ions accelerated using electric field
• Accelerated to have same KE
• velocity depends on mass
~ lighter ions will move faster
Ion Drift in TOF MS
• Ions pass though negatively charged plate and into flight tube
• Time of flight depends on velocity
Detection for TOF MS
• Once through mass spectrometer, 1+ ions hit negatively charged detector plate
• As they hit plate they gain e
• This discharges ion and produced current
• Size of current proportional to abundance of ions
Number of orbitals in each subshell
s: 1 orbital, 2e
p: 3 orbitals, 6e
d: 5 orbitals, 10e
f: 7 orbitals, 14e
s, d, p, f blocks
Left s
Middle d
Right p
Bottom f
Energy of orbitals and shells
• Shells increase in energy
s < p < d < f
~ Exception is 3d is higher than 4s
• Orbitals in same subshell has same energy
Exceptions
Cu
[Ar] 3d^5 4s^1 NOT [Ar] 3d^4 4s^2
Cr
[Ar] 3d^10 4s^1 NOT [Ar] 3d^9 4s^2
• The unexpected configurations are more stable
• 4s orbital filled b4 3d orbital
Define 1st IE
Energy required to remove one mol of e from one mol of atoms of an element to form one mol of 1+ ions
Tend in IE
1st IE increased by :
• Increase of nuclear charge
~ atomic radius decreases so outer e closer
• Shielding is constant
• Harder to remove e
• Affected by spin-pair repulsion
• 1st IE increases across periodic table and decreases down group
Dips in trend
• Slight decrease in IE1 between G2 and G3
~ G3 outer e in p subshell which further from nucleus than G2 outermost e which is in s subshell
• Decrease in IE1 from G5 to G6
~ Spin pair repulsion in 2p^x orbital of G6 so repulsion between those e makes it easier to remove
From one period to next
• Large decrease
• Added shell so increased distance between nucleus and outer e
• Increased shielding from this
• This outweighs increased nuclear charge
IE down group
• Decreases
• Nuclear charge increased
• Distance between nucleus and outer e increase
• Shielding increases
• Outweigh nuclear charge easier to remove outer e
Successive IE
• Increase
• Once e removed positive ion
• More difficult to remove e
~ decreased shielding, increase in proton to e ratio
• Not consistent
