Periodic table

• Atomic number


  No. of protons (same as no. of electrons)
• Mass number


  No. of protons + neutrons
• Groups


  • Same no. of electrons in outer energy level
• Group 1 Alkali metals


  • Very reactive
• Periods


  • Fire
  • Earth
  • Wind
  • Water
• Greeks first defined the concept of elements
• Boyle defined an element as a substance which cannot be broken down into simpler substances by chemical means
• Davy discovered potassium by passing electricity through a compound of potassium
• Cations


  Lose electrons
• Mendeleev left gaps in his periodic table for undiscovered elements
• Transition metals


  • Variable valency
  • Good catalysts
  • Form coloured ions
• Anions


  Gain electrons
• Mercury and bromine are the only liquid elements
• Mass Spectrometry


  • Uses: drugs, exhaust fumes, quality control
  • Principle: movement of charged particles in a magnetic field being deflected to different extents according to their masses
• Mass Spectrometry


  1. Vaporisation

  2. Ionisation

  3. Acceleration

  4. Separation

  5. Detection
• Law of octaves


  Arrangements of elements in which the first and the 8th element, counting from a particular element have similar properties.
• Isotope 


  These are forms of an element which have the same atomic number but different mass number. Same number of protons but different neutrons.
• Triads


  Is a group of 3 elements where the atomic weight of the middle element is approx. equal to the average of the other 2.
• Atomic mass


  Number of protons and neutrons in an atom.
• Element


  A substance that cannot be broken down into simpler substances by chemical means.
• What happens during vaporisation?


  Sample is injected and liquid sample is vaporised as the inside is a vacuum
• What happens during ionisation?


  Electron gun shoots electrons at atoms/ molecules, knocking out electrons to form cations
• What happens during acceleration?


  Positive repeller moves positive ions towards negative acceleration plate. A narrow stream of ions pass into the separation unit.
• What happens during separation?

  Ions are separated on the basis of their mass.
• What happens during detection?


  Ions are detected and info is fed to a computer for analysis.
• Relative atomic mass


  The average of the mass numbers of the isotopes of the element. They occur naturally. They take abundances into account. They are expressed on the scale in which atoms of the carbon-12 isotope have a mass of exactly 12 units.
• Simple rhythm for mass spec.

  Vodka Is A Strong Drink
• First ionisation energy 


  The energy required to remove the most loosely bound electron from the atom.
• Valency: the number of atoms of hydrogen or any other monovalent element with which each atom of the element combines.
• Electronegativity: the force of attraction which an atom has for the shared pair of electrons in a covalent bond.