chapter 1

chapter 1

1. atoms

   • proton
     • mass= 1
     • charge = +1
   • neutron
     • charge = 0
     • mass = 1
   • electron
     • mass = 1/1836
     • charge = -1
   • ISOTOPES have the same number of protons and electrons but different numbers of neutrons
   • MASS NUMBER gives the number of sub atomic particles in the nucleus
   • ATOMIC NUMBER is the number of protons in the nucleus

2. mass spectrometer

   • ionisation
     • a high energy beam of electrons are fired from an electron gun to knock off one e- leaving an ion with a uni-posative charge
   • vapourisation
     • the sample needs to be gaseous to be ionised and to travel through the mass spec
   • acceleration
     • so that the ions travel through the mass spec they are accelerated by an electric field, causing them to move very quickly through the mass spec and causing them to be fouced into a narrow beam
   • deflection
     • magnetic field deflects lighter ions more than heavier ions, only the ions with the correct m/z will be deflected round the bend of the mass spec
   • detection
     • the +ve ions hit the -ve detector and create a current which is recorded as a signal on the mass spectrum
   • RELATIVE ISOTOPIC MASS= mass of one atom of the isotope / mass of one atom of Carbon (12) x12
   • the mass spectrum shows the relative abundances of each ion
   • the tallest peak is the base peak

3. arranging electrons

   • s sub level = 2 e-
   • p sub level = 6 e-
   • d sub level = 10 e-
   • each orbital can hold a maximum of 2 electrons, when 2 electrons occupy one orbital they must have opposite spins
   • copper = [Ar]3d10 4s1
     • chromium = [Ar] 3d5 4s1
   • atoms may gain or lose electrons in a reaction, then they're ions
     • ions which have the same electron configuration as other atoms are said to be isoelectronic

4. evidence for energy levels

   • ionisation energy
     • an endothermic process
     • general equation = M -> M+ + e-
   • groups
     • the first ionisation energy decreases as you go down the group
     • as the distance from the nucleus to the outer electrons increase resulting in them being less strongly attracted to the nucleus
       • this is despite an increased nuclear charge
   • periods
     • first ionisation increases across periods
       • as a result of increased stability
     • abruptly decrease at the start of a new period

5. evidence for sub-levels

   • first ionisation
     • shows a general increase
       • drops at...
         • start of p block as a new sub shell is started to be filled
         • betweenp3 and p4 as the electrons start pairong up and causes repulsion