Periodicity

• The periodic table is organised by atomic number, which is the number of protons in an atom.
• groups (top to bottom )- vertical columns within the table contain elements with similar chemical properties resulting from the same number of outer electrons
• periods (right to left) - rows of elements arranged in increasing atomic number, increasing number of outer electrons
• Activation energy

  the minimum energy required for a reaction to occur
• activated complex

  an unstable arrangement of atoms formed at the maximum of the potential energy barrier
• $delta$H


  change in enthalpy
• catalyst 


  alters the rate of a chemical reaction allowing it to be done at a lower temperature
• covalent radius

  determined by measuring half the distance between the two nuclei of the two covalently bonded atoms
• Across the period

  covalent radius decreases duo to an increase in nuclear charge
• down the group

  covalent radius increases due to a decrease in nuclear charge
• First covalent moleculars

  Hydrogen, Nitrogen, Oxygen, flourine, chlorine, phosphorus, sulfur
• First covalent networks

  Boron, Carbon, SIlicon
• First metalics

  Lithium, Beryllium, Sodium, Magnesium, Alluminium, Potassium, Calcium
• First monatomics


  Helium, Argon, Neon