Periodicity

• periodicity- the repeating of patterns/trends of physical or chemical properties
• atomic radius decreases across period 3;

  • outer electrons in the same energy level
  • same shielding on the outer electrons
  • proton number increases
• electronegativity- the power of an atom to pull the electron density in a covalent bond towards itself
• Electronegativity increases across period 3:

  • proton number increases
  • atomic radius decreases so bonding pair closer to nucleus
  • electron pair in covalent bond more attracted to atom's nucleus
• Electronegativity increases up a group:

  • atoms get smaller
  • nucleus closer to bonding pair of electrons
  • so stronger attraction
• Ionisation energy- energy required to remove one mole of electrons form one mole of gaseous atoms
• Ionisation energy increases across period 3:

  • atomic radius decreases
  • proton number increases
  • therefore, greater attraction between nucleus and outer shell electrons