atomic structure

• whats a mass number ?


  total number of protons and neutrons in the nucleus
• whats the atomic number?


  the number of protons in the nucleus
• whats a isotope?


  atoms of the same element with the same number of protons but different number of neutrons

  • isotopes have the same configuration of electrons so they have got the same chemical properties, they have different physical properties such as rates of diffusion or densities because physical properties depend on the mass of the atom
• how many orbitals are in a s-orbital ?


  1
• whats the maximum amount of electrons in a s-sub shell?


  2
• how many orbitals are in a p-subshell?


  3
• whats the maximum amount of electrons in a p-subshell?


  6
• how many orbitals are in a d-subshell?


  5
• whats the maximum amount of electrons in a d-subshell?


  10
• how many orbitals are in a f-subshell?


  7
• whats the maximum amount of electrons in a f-subshell?


  14
• whats the first ionisation energy?


  the energy needed to remove 1 electron from each atom in 1 mole of gaseous atoms to form 1 mole of gaseous 1+ ion
• what does high ionisation energy mean?


  there is a high attraction between the electron and the nucleus and so more energy is needed to remove the electron
• whats the second ionisation energy?


  the energy needed to remove 1 electron from each ion in 1 mole of gaseous 1+ ions to form 1 mole of gaseous 2+ ions
• what are the three factors affecting ionisation energy?

  nuclear charge

  distance from nucleus

  shielding
• why does nuclear charge affect ionisation energy?


  the more protons there are in the nucleus, the more positively charged the nucleus is and the stronger the attraction to the electrons
• why does distance from the nucleus affect ionisation energy?


  attraction falls of very rapidly with distance. an electron close to the nucleus will be much more strongly attracted than one further away.
• what is shielding?


  the lessening of the pull of the nucleus by inner shells of electrons
• why does shielding affect ionisation energy ?


  as the number of electrons between the outer electrons and the nucleus increases, the outer electrons fell less attraction towards the nuclear charge
• what did john Dalton think about the atom?


  he though atoms were spherical and different spheres constituted different elements. he also thought that they were invisible.
• what did jj Thompson discover about the atom?


  he discovered that atoms are divisible, he discovered and measured the mass of the electron which made him discover that there is smaller particles inside the atom leading to the plum pudding model. this model is a large positively charged sphere with embedded negatively charged electrons.
• what did Ernest Rutherford discover about the atom?


  Ernest Rutherford fired alpha particles at a thin film of gold where most particles passed straight through. this led the nuclear model to be viewed as being mostly empty space, with a positive nucleus and orbiting electrons
• what did Neil Bohr discover about the atom?


  he discovered that electrons orbit at fixed orbits of defined energy and that they must emit or absorb electromagnetic radiation of a particular frequency.
• what is electron bombardment?

  • for atoms and small molecules
  • sample is vaporised
  • high energy electrons are fired at the sample
  • an electron is knocked off each atom
• what is electrospray ionisation?

  • for larger molecules
  • sample is dissolved in a solvent
  • it is injected through a nozzle at high voltage
  • gains a proton
  • both create positive ions
• what 4 things happen when a sample is squirted into a time of flight mass spectrometer?

  1. ionisation - electrospray ionisation and electron impact ionisation
  2. acceleration
  3. ion drift
  4. detection
• whats electron impact ionisation?

  the sample is vaporised and an electron gun is used to fire high energy electrons at it.

  this knocks one electron off each particle so they become +1 ions
• what is acceleration in the mass spectrometer?

  positive ions attracted towards a negatively charged plate / electric field. all have the same kinetic energy.
• what is drift in mass spectrometry?

  ions drift through a vacuum chamber, lower mass ions move faster. it is a vacuum to avoid other things being detected in the air.
• how are charged particles detected?

  • positive ions strike a detector plate and each gain an electron.
  • a current forms as electrons flow
  • the current size is proportional to the number of ions hitting the plate
• what are the trends in first ionisation energy?

  • the first ionisation energies of elements down a group of the periodic table decrease
  • the first ionisation energies of elements across a period generally increase
• whats relative atomic mass?

  the mean mass of an atom of an element , divided by one twelfth of mean mass of an atom of the carbon 12 isotope
• how are ions formed?

  when an atom loses or gains electrons meaning it is no longer neutral and will have an overall charge
• whats mass spectrometry?


  an analytical technique used to identify different isotopes and find the overall relative atomic mass of an element
• whats the time of flight mass spectrometry?

  form of mass spectrometry that records the time it takes for ions of each isotope to reach a detector. using this a spectra can be produced showing each isotope present
• what is the relative atomic mass?

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

  the mass of an atom of an isotope of an element on a scale where an atom of carbon 12 is 12
• what is the relative molecular mass?

  the average mass of a molecule on a scale where an atom of carbon 12 is 12
• whats an orbital ?

  a volume of space in an atom which can hold 2 electrons - it is represented by a box
• whats a sub level?

  a group of orbitals at a fixed energy level - with the letters of s, p, d, f