Atomic structure
22 January 2024 16:43
• Isotopes: Atoms of the same element with a different number of neutrons
• RAM: Weighted mean mass of an atom of an element relative to 1/12th the mass of a 12C atom
• RIM: Mass of an atom of an isotope relative to 1/12th the mass of a 12C atom
Relative formula mass (for giant compounds) and Relative molecular mass (Mr): Calculated by
adding all of the relative atomic masses of the atoms in the formula
Electron configurations and shells:
Electron configuration for Calcium: 1s22s22p63s23p64s2
Electron in box configuration for titanium:
Orbital: Area or region in an atom where it is likely to find an electron
s: 1 orbital (hollow sphere)
p: 3 orbitals (dumbbell shaped)
d: 5 orbitals
f: 7 orbitals
• In orbitals, electrons spin against each other (causing a repulsion)
• Orbitals fill up singly before electrons pair up
• p orbital with 4 electrons:
Evidence for shells using emission spectra:
• Electrons release energy by dropping from a highe
energy level to a lower one, energy is released in th
form of light.
• This proves that shells are present due to the differ
wavelengths of light
,
,Mass Spectrometry and Ionisation Energies
22 January 2024 16:44
Mass Spectrometer
• Each of the m/z values represent an isotope and the height represents it's
abundance
( ∗ )+( ∗ )…
• We can calculate RAM: Ar=
Example:
, • Ratio is 9:6:1, this is shown by the peaks in the
spectrum
Mass spectra for organic compounds:
• Organic compounds undergo fragmentation:
Butane:
Methylpropane:
• The butane molecule fragmented into many ions of different
masses
• Mr of butane: 58 (M peak)
• Most stable fragment at m/z = 43
• How would the spectrum change if the compound was
methylpropane:
• Different peaks because fragmentation would be different, bonds
break in other places of the molecule causing different Mr values
• Same Mr
Ionisation Energies:
First ionisation energy: Energy required to remove one electron from each atom in
one mole of gaseous atoms to from 1 mole of gaseous 1+ ions.
Equation:
Each successive ionisation energy requires
First: Ca (g) → Ca+ (g) + e- IE1 = +590 kJ mol-1 more energy because electrons are removed
Second: Ca+ (g) → Ca2+ (g) + e- IE1 = +1145 kJ mol-1 from an increasingly positive ion
Third: Ca2+ (g) → Ca3+ (g) + e- IE1 = +4912 kJ mol-1
Factors that affect ionisation energy:
• Shielding: Inner electrons in the atom shield outer electrons from the nuclear pull. More
shielding makes removing electrons easier
• Nuclear pull: As the number of protons increases, so does the attraction the electrons have
towards them. A greater nuclear pull makes removing electrons harder
• Nuclear distance: The further electrons are form the nucleus, the less they will be affected by
the nuclear pull. Electrons that are further from the nucleus are more easily removed
Down a group:
• Ionisation energy decreases:
22 January 2024 16:43
• Isotopes: Atoms of the same element with a different number of neutrons
• RAM: Weighted mean mass of an atom of an element relative to 1/12th the mass of a 12C atom
• RIM: Mass of an atom of an isotope relative to 1/12th the mass of a 12C atom
Relative formula mass (for giant compounds) and Relative molecular mass (Mr): Calculated by
adding all of the relative atomic masses of the atoms in the formula
Electron configurations and shells:
Electron configuration for Calcium: 1s22s22p63s23p64s2
Electron in box configuration for titanium:
Orbital: Area or region in an atom where it is likely to find an electron
s: 1 orbital (hollow sphere)
p: 3 orbitals (dumbbell shaped)
d: 5 orbitals
f: 7 orbitals
• In orbitals, electrons spin against each other (causing a repulsion)
• Orbitals fill up singly before electrons pair up
• p orbital with 4 electrons:
Evidence for shells using emission spectra:
• Electrons release energy by dropping from a highe
energy level to a lower one, energy is released in th
form of light.
• This proves that shells are present due to the differ
wavelengths of light
,
,Mass Spectrometry and Ionisation Energies
22 January 2024 16:44
Mass Spectrometer
• Each of the m/z values represent an isotope and the height represents it's
abundance
( ∗ )+( ∗ )…
• We can calculate RAM: Ar=
Example:
, • Ratio is 9:6:1, this is shown by the peaks in the
spectrum
Mass spectra for organic compounds:
• Organic compounds undergo fragmentation:
Butane:
Methylpropane:
• The butane molecule fragmented into many ions of different
masses
• Mr of butane: 58 (M peak)
• Most stable fragment at m/z = 43
• How would the spectrum change if the compound was
methylpropane:
• Different peaks because fragmentation would be different, bonds
break in other places of the molecule causing different Mr values
• Same Mr
Ionisation Energies:
First ionisation energy: Energy required to remove one electron from each atom in
one mole of gaseous atoms to from 1 mole of gaseous 1+ ions.
Equation:
Each successive ionisation energy requires
First: Ca (g) → Ca+ (g) + e- IE1 = +590 kJ mol-1 more energy because electrons are removed
Second: Ca+ (g) → Ca2+ (g) + e- IE1 = +1145 kJ mol-1 from an increasingly positive ion
Third: Ca2+ (g) → Ca3+ (g) + e- IE1 = +4912 kJ mol-1
Factors that affect ionisation energy:
• Shielding: Inner electrons in the atom shield outer electrons from the nuclear pull. More
shielding makes removing electrons easier
• Nuclear pull: As the number of protons increases, so does the attraction the electrons have
towards them. A greater nuclear pull makes removing electrons harder
• Nuclear distance: The further electrons are form the nucleus, the less they will be affected by
the nuclear pull. Electrons that are further from the nucleus are more easily removed
Down a group:
• Ionisation energy decreases:
