Periodicity

• Elements are ordered by proton number, not mass number, in the periodic table
• Groups


  Columns in the periodic table, elements in the same group have the same number of electrons in their outer shell
• Periods


  Rows in the periodic table, elements in the same period have the same number of electron shells
• Periodic table element blocks

  • S-block
  • P-block
  • D-block
  • F-block
• Metallic bonding


  Positive metal ions with delocalized electrons surrounding them
• As metallic charge increases

  Melting point increases
• Covalent bonding

  Many strong covalent bonds holding atoms together in a giant structure
• Simple molecular structure

  Small molecules held together by weaker van der Waals forces
• As molecular size increases

  Melting point increases
• Ionization energy


  Minimum energy required to remove one mole of electrons from one mole of atoms in the gaseous state
• As atomic radius increases down a group


  Ionization energy decreases
• As atomic number increases across a period

  Ionization energy increases
• Shielding


  Protection of inner electron shells from the nucleus
• As shielding increases down a group


  Ionization energy decreases
• As electron repulsion increases within an orbital


  Ionization energy decreases
• The periodic table is arranged by proton number, not mass number
• Elements in the same group have similar properties and react in similar ways
• Elements in the same period have the same number of electron shells
• The periodic table is divided into s-block, p-block, d-block and f-block elements
• Atomic radius decreases across a period due to increased nuclear charge
• Atomic radius increases down a group due to more electron shells
• Metallic bonding involves positive metal ions and delocalized electrons
• Covalent bonding involves many strong bonds in a giant structure
• Simple molecular structures are held together by weaker van der Waals forces
• Ionization energy is the minimum energy required to remove an electron from an atom
• Ionization energy decreases down a group due to increased shielding and atomic radius
• Ionization energy increases across a period due to increased nuclear charge
• Electron repulsion within an orbital can decrease ionization energy
• Periodicity is the trend in the properties of elements across a period
• trends melting points for period 3:

  • first 3 elements na mg and AL have metallic bonding
  • general increase in melting points - increasing positive charge, increasing number of delocalised electrons, so stronger metallic bonding
• what element has the highest melting point in group 3


  silicon - has a macromoleular structure
• phosphorus has a lower melting point than silicon due to a weaker simple molecular structure and so weaker vdw forces
• what element has the lowest melting point


  argon - smaller vdw forces
• ionisation energy generally increases across a period:

  nuclear charge increases

  shielding stays similar

  atomic radius decreases
• smaller nuclear charge = larger atomic radius