Atomic structure Flashcards
Isotopes
same no of protons but different no of neutrons
Electron impact
- Vapourised sample injected at low pressure
- Electron gun fires high energy electrons at sample
- Knocks out an outer electron
- Forming +ve ion with different charges (Ti—>Ti+ +e-)
Electrospray ionisation
- sample dissolved in volatile,polar solvent
- Injected through fine needle gives aerosol
- tip of needle high voltage ,gains proton(H+)
- MH+ ion moves towards negative plate
Acceleration
Positive ions are accelerated by an electric field
velocity dependant on mass
Flight tube
Positive ions with smaller m/z values ahve the same kinetic energy as those with larger m/z values & will move faster
Detection
Ions reach detector and generate a small current which is fed to a computer for analysis
Relative atomic mass
Isotope mass x % percentage abundance/ 100
Forming ions
Loose 4s before 3d
Cr and C u
Only 4s 1 in 4s shell
First ionisation energy
enthalpy change when 1 mole of gaseous atom forms ! mole of gaseous ion with a positive ion
Second ionisation energy
enthalpy change when one mole of gaseous ions with a single positive charge forms one mole of gaseous
ions with a double positive charge
Factors affecting ionisation energies
- Attraction of nucleus
- The distance of the electrons from nucleus
- Shielding of the electrons from nucleus
Why is there a small drop from Mg to Al ?
Al is starting to fill a 3p shell where as Mg has its outer electron in 3s sub shell.3p easier to remove less sheilding
Why has Na a much lower first ionisation energy that
Neon?
Na will have its outer electron in a 3s shell further from the nucleus and is more shielded.easier to remove & lower first ionisation energy
Why is there a small drop from form P to S shell?
S has 4 electron the 4th is filling doubly the 1st
slight repulsion by the negatively charged electron making the 2nd easier to remove
