Atomic structure

• Concordant results


  Results within 0.1 of each other
• Electrons


  • Mass 1/1000
  • Negative charge 1/1820 of a
• Electron configuration


  1. 2 on inner shell

  2. 8 on rest

  3. Transition metals have 1 on one shell and 36 on another
• Shared, lost, gained


  Referring to electrons
• Energy level cross section

  
• S sub level


  Max 2 electrons
• P sub level


  Max 6 electrons
• D sub level


  Max 10 electrons
• F sub level


  Max 14 electrons
• 1. orbital


  The area the electron could be
• Copper and chromium are exceptions when filling in the energy levels
• Ionisation across a period

  Increases except at group 3 or 5
• Group 3 exception because


  Electron is lost on different energy level
• Group 5 exception because

  Electron is lost due to mutual repulsion
• DENS

  • Distance
  • Electron lost
  • Nuclear charge
  • Shielding
• Ionisation down a group 


  Decreases due to distance and shielding
• Electron impact ionisation


  1. Vapourised sample being

  2. High energy electron fired at it

  3. Electron is knocked off forming negative ion

  4. Negative ion attracted to positive electric plate

  5. Accelerated through the machine
• Electron impact ionisation


  Used for low mass elements
• Ionisation (electrospray)


  1. Sample dissolved in volatile solvent

  2. Solvent injected by needle of high voltage supply

  3. Tip of needle is ionised by gaining a proton

  4. Solvent becomes ionised mist

  5. Ionised sample travels through machine
• Ionisation (electrospray)


  Also called 'soft ionisation'
• Acceleration and ion drift

  1. Positive ions accelerated using electric field

  2. Velocity of particles depends on mass

  3. Lighter particles have smaller velocity

  4. All particles have same kinetic energy
• Detection


  1. Positive ions hit detector plate

  2. Gaining electrons causes current spike

  3. Bigger the peak, more ions detected

  4. Helps determine formula mass
• Time of flight= d/v
• Ke= 1/2(mv^2)
• Time a= root of (timeb^2 x massa/massb)
• Which letter is used to represent the atomic number of an atom?

  Z
• What does the atomic number tell us about an element?

  It indicates the number of protons in an atom.
• What letter represents mass number?

  A
• How is the mass number calculated?

  Mass number = number of protons + number of neutrons.
• Define relative atomic mass.

  It is the average mass of all isotopes of an element compared to ¹/₁₂ the mass of an atom of Carbon 12 (C¹²).
• What are isotopes of an element?

  Isotopes are different forms of the same element, containing the same number of protons but different numbers of neutrons.
• How many orbitals and electrons do the following shells contain?

  • 1s: 1 orbital, 2 electrons
  • 2p: 3 orbitals, 6 electrons
  • 3s: 1 orbital, 2 electrons
  • 3d: 5 orbitals, 10 electrons
  • 4s: 1 orbital, 2 electrons
• Does 3d or 4s have a higher energy?

  3d has a higher energy than 4s.
• What is an orbital?

  An orbital is a region around the nucleus that can hold up to two electrons.
• What would be the relationship between 2 electrons in the same orbital in terms of their spin?

  They have opposite spin as they repel each other due to both being negative.
• Explain why chromium does not fit the trend for electronic configuration.

  Chromium has one electron in its 4s orbital before filling 3d.
• Explain why copper does not fit the trend for electronic configuration.

  Copper has one electron in its 4s orbital before filling 3d.
• What are the two types of ionisation for a mass spectrometer and how do they differ?

  1. Electron impact:

  • Uses an electron gun to knock off one electron from each particle, forming 1+ molecular ions that can fragment.

  1. Electrospray:

  • Sample is dissolved in a solvent and injected to form an aerosol, gaining a proton from the solvent, producing XH+ ions without fragmentation.
• When would you use the different types of ionisation in a mass spectrometer?

  Electron impact is used for organic or inorganic molecules with low formula mass, while electrospray is used for higher molecular mass substances like proteins.
• Describe how a time of flight mass spectrometer works.

  1. Acceleration: Positive ions are attracted towards a negatively charged plate.
  2. Ion Drift: Ions pass through a hole, forming a beam with constant kinetic energy, traveling to the detector; time of flight is proportional to the square root of mass.
  3. Detection: Ions pick up electrons, current flows, and m/z value and time of flight are recorded.