Atomic Structure Flashcards
(12 cards)
Define relative atomic mass
The average mass of all an elements isotopes relative to 1/12 the mass of a carbon 12 atom.
How many orbitals and electrons does a 3d shell contain?
3 orbitals, 6 electrons
Does 3d or 4s have higher energy?
3d
What are the two exceptions to the 4s/3d rule.
Chromium and copper take only 1 electron into 4s because the atom is more stable with either a half full or entirely full 3d shell
Describe electrospray ionisation
- sample dissolved in volatile solved
- injected through fine hypodermic needle
- needle is attached to a high- voltage power supply and particles gain a proton from the solvent
- x~>XH* (1+ charge and mass of Mr +1)
- rarely fragment
- high mass biological molecules
Describe electron impact ionisation
- electron gun fires high energy electrons at the sample which knocks off one electron from each particle to form 1+ ions
- organic or inorganic with low mass
Describe how a TOF mass spectrometer works
Acceleration: positive ions attracted to negative plate
Ion drift: Ions pass through hole in plate and form a beam with constant kinetic energy
Detection: positive ions gain electrons at the detector, current flows, M/Z value proportional to abundance of ions
Define first ionisation energy
The energy required to remove 1 mole of electrons from 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ions
Why are second ionisation energies higher than first ionisation energies?
The electron is being removed from a positive ion and is colder to the nucleus so therefore requires more energy
What accelerates the ionised particles in TOF spectroscopy?
An electromagnet
Why does aluminium have a smaller first ionisation energy than magnesium?
The Al electron is in a 3p orbital whereas mg is in 3s. 3p has greater energy so is further from the nucleus.
How are particles and their abundance detected in TOF spectroscopy
Electrons flow from the detector to the ions
