Atomic Structure Flashcards
what does an atom consist of and what are the charges and mass
nucleus - charge 0 - mass 1
proton - charge 1 - mass 1
electron - charge -1 - mass 0
what is the mass number
Mass number = number of protons + number of neutrons
what is proton number
Number of protons = mass number - number of neutrons
what is an isotope
an atom with same number of protons and electrons but different number of neutrons
what is electron impact
- for small molecules
- high energy electrons from electron gun fired at sample
- knocks off one electron (repulsion)
- has to happen in the gas phase
what is electrospray
- for large molecules
- sample dissolved in volatile solvent injected as an aerosol through needle
- needle has a high positive charge
- sample gains a H+ ion
what is acceleration TOF
- positive ions are accelerated by an negative electric field
- to a constant kinetic energy
what is ion drift TOF
the positive ions with smaller m/z values travel faster than those with larger m/z values as they have the same kinetic energy
what is detection TOF
- for each isotope the mass spectrometer can measure a m/z ratio and abundance
- each ion of the same mass hits the detector at the same time and each ion gains an electron
- this flow of electrons is a current that is measured and is proportional to abundance
what does TOF mean
time of flight
what is mass spectrometry used to do
- identify elements
- identify relative molecular mass
what is m/z
mass charge ratio
what is first ionisation energy
the minimum energy requirement to remove 1 mole of electrons from 1 mole of gaseous atom to form 1 mole of gaseous ions under standard conditions
what is trend in first ionisation energy across period
- increased nuclear charge
- atoms get smaller
- stronger attraction from nucleus to valance electrons
what causes deviation in group 3
e.e. Al decreases because it has the first electron in 3p which is higher in energy than 3s
