ATOMIC STRUCTURE

• What is the mass of an electron?


  1/1836
• Why do isotopes have the same chemical properties?

  Same electron configuration
• Orbitals


  regions of space in which electrons are most likely to be in (it is impossible to tell for certain where an electron is/ where it is going)
• • electrons are arranged in shells
  • each shell consists of 1 or more orbitals
  • each orbital contains a maximum of 2 electrons
  • 4 types of orbital: s p d f
• How many orbitals in s subshell?


  1
• How many orbitals in p subshell?


  3
• How many orbitals in d subshell?


  5
• What’s the maximum number of electrons in s subshell?


  2
• What’s the maximum number of electrons in p subshell?


  6
• What’s the maximum number of electrons in d subshell?


  10
• Why does 3s come before 3p?


  s orbital always have a lower energy level than p orbitals at the same energy level so the s orbital always fills with electrons before the corresponding p orbital
• Why does 4s come before 3d?


  Energy levels are filled in order of increasing energy, and the 4s orbital has a slightly lower energy than the 3d orbital.
• What is the electorn configuration of Chromium Cr?


  1s2 2s2 2p6 3s2 3p6 4s1 3d5
• What is the electorn configuration of Copper Cu?


  1s2 2s2 2p6 3s2 3p6 4s1 3d10
• Mass Number


  total amount of protons and neutrons in one isotope
• Relative Atomic Mass


  average mass of an atom of an element compared to 1/12 of the mass of Carbon-12
• Electron Impact

  • electron gun
  • fires high energy electron
  • knocks off an electron from each particle
  • X(g) → X+(g) + e-
• Electrospray ionisation

  • sample dissolved in volatile solvent
  • injected through a fine hypodermic needle giving a fine mist
  • tip of needle has high voltage
  • each particle gains a proton
  • X(g) + H+ → XH+(g)
• Acceleration

  • positive ions are accelerated using and electric field
  • they all have the same kinetic energy
  • KE = 0.5mv^2
• Ion Drift

  • time of flight of each particle depends on its velocity which depends on its mass
  • lighter isotopes travel faster
  • d=vt
• Detection

  • positive ions gain an electron at negatively charged detector plate
  • creates an electric current
  • electric current is directly proportional to abundance of isotopes
  • computer produces mass spectrum
• How would you get the mass of an atom using Avogadro's number?


  mass x10^-3/ 6.022 x10^23
• number of peaks = number of isotopes
• In m/z what does m stand for?


  mass
• In m/z what does z stand for?


  charge (usually given or +1)
• 1st ionisation energy

  • energy required to remove the outermost electron
  • from one mole of atoms to form one mole of 1+ ions
  • all species in gaseous state
  • X(g) → X+(g) + e-
• How does atomic radius impact ionisation energy?


  as distance between outermost electron and nucleus increases, the attraction between them decreases
• How does shielding impact ionisation energy?


  a greater number of shells means less attraction between outermost electro and nucleus
• How does nuclear charge impact ionisation energy?


  a greater number of protons means stronger attraction between outermost electrons and nucleus
• Explain why He’s 1st ionisation energy is much higher than Ne:

  • He has a smaller radius than Ne
  • He has less shielding than Ne
  • He has a stronger attraction between outermost electron and nucleus
• Explain why N has a higher 1st ionisation energy than C:

  • N has a smaller radius than C
  • N has more shielding than C
  • N has a higher nuclear charge than C
  • N has a stronger attraction between outer electrons and nucleus
• What happens to the atomic radius across a period?


  it decreases because elements gain more protons and have the same shielding so nucleus attracts electrons more strongly
• Explain why Mg’s 1st ionisation energy is more than Al’s:

  • Mg’s outermost electron is in 3s
  • Al’s outermost electron is in 3p
  • 3p is higher in energy than 3s so it is further away from nucleus
  • stronger attraction between Mg’s outermost electron and Mg’s nucleus
• Explain why N’s 1st ionisation energy is more than O’s:

  • N’s outermost electron is in 2p3
  • O’s outermost electron is in 2p4
  • electron pair repulsion in O goes away
  • O’s ionisation energy is lower than expected
• Why is there a big jump in ionisation energy moving from 3rd shell to 2nd shell?


  2nd shell is closer to nucleus so stronger attraction between nucleus and outermost electron