atomic structure revision MOCKS

• relative mass proton


  1
• relative charge proton


  +1
• relative mass neutron


  1
• relative charge neutron


  0
• relative mass electron 


  1/2000
• relative charge electron 


  -1
• mass number symbol?


  A
• atomic (proton) number symbol?


  Z
• element symbol?


  X
• isotopes?


  isotopes of an element are atoms with the same number of protons but different numbers of neutrons.
• what decides chemical properties of an element?


  number and arrangement of electrons
• how do properties of elements change?

  • isotopes have slightly different physical properties, eg: density bc/ physical properties depend on mass of the atom.
  • isotopes have same configuration of electrons so same chemical properties.
• what was John Dalton's atomic model like?


  • solid spheres
  • diff spheres make up diff elements
• what was jj Thomson's atomic model like?


  • discovered the electron
  • atoms aren't solid and indivisible
  • Plum Pudding Model
• what was Rutherford's atomic model like?


  • gold foil experiment
  • discovered most of the atom was empty space
  • Nuclear Model
• describe the alpha particle experiment


  • fired positively charged alpha particles at thin sheet of gold
  • plum pudding model suggested most alpha particles would be deflected by the positive sphere
  • most of the particles passed straight through, only a few deflected
  • So, the atom is a tiny positively charged nucleus surrounded by a cloud of negative electrons, most of atom is empty space
• what was Niels Bohr's atomic model like?


  • elections exist in shells of fixed energy
  • when electrons move between shells, electromagnetic radiation with fixed energy is emitted or absorbed.
  • the Bohr Model
• why is the Bohr Model still used today?


  its simple and explains many experimental observations, like bonding.
• what is relative atomic mass (Ar)


  the average mass of an atom of an element where an atom of carbon 12 is 12.
• what is relative isotopic mass?


  the mass of an atom of an isotope on a scale where an atom of carbon 12 is 12.
• what is relative molecular mass (Mr)


  the average mass of a molecule on a scale where an atom of carbon 12 is 12
• what can a mass spectrometer tell us?


  • relative atomic mass
  • relative molecular mass
  • relative isotopic abundance
• what is step 1 of mass spectrometry?


  Ionisation. 2 ways - electro spray ionisation or electron impact.
• describe electrospray ionisation


  sample is dissolved and pushed through a nozzle at high pressure. High voltage is applied to it, causing each particle to gain a H+ ion. Sample is turned into a gas made of positive ions.
• describe electron impact


  sample is vaporised and an electron gun fires high energy electrons at it, this knocks one electron off each particle so they become 1+ ions.
• what is step 2 of mass spectrometry?


  Acceleration. Positively charged ions are accelerated by an electric field so they have the same kinetic energy.
• what is step 3 of mass spectrometry?


  Ion Drift. The ions enter a region with no electric field, they just drift through it. Lighter ions drift through faster than heavier ones.
• what is step 4 of mass spectrometry?


  Detection. Lighter ions travel at higher speeds in the drift region, so they reach the detector faster than heavier ions. The detector detects charged particles and a mass spectrum is made.
• what is the mass spectrum?


  • y axis = abundance of ions.
  • x axis = mass/charge ratio
  • if the sample if an element, each line represents a different isotope of the element.
• how to calculate relative atomic mass from mass spectrum?

  1. for each peak, read the abundance from y axis and the mass from the x axis. Multiply them together to get t total mass for each isotope. mass x abundance.
  2. add up the totals
  3. divide by 100 if % or the sum of abundances if not a %.
• how can you identify molecules from mass spectrometry?

  1. a molecular ion (m+) is formed in the mass spectrometer when one electron is removed from the molecule.
  2. this creates a peak the spectrum with a mass/charge ratio equal to the relative molecular mass of the molecules.
  3. this can be used to help identify an unknown compound.
  4. the mass/charge figure is equal to the Mr.
• what do electrons have in the current accepted model?


  electrons have fixed energies. They move around the nucleus in certain regions of the atom called shells or energy levels.
• what is each shell given?

  a principal quantum number.
• how do principal quantum numbers work?


  the further a shell is from the nucleus, the higher its energy and the larger its principal quantum number.
• what do experiments on electron shell energy show?


  not all electrons in a shell have exactly the same energy. Shells are divided into sub-shells that have slightly different energies. The sub-shells have different numbers of orbitals, that can hold up to 2 electrons.
• how many orbitals does sub shell 's' have?


  1 orbital.
• what is the max number of electrons the 's' sub-shell can have?


  1 x 2 = 2
• how many orbitals does sub-shell 'p' have?


  3 orbitals.
• what is the max number of electrons the 'p' sub-shell can have?


  3 x 2 = 6
• how many orbitals does sub-shell 'd' have?


  5 orbitals.