PERIODICITY

PERIODICITY

1. Atomic Radius

   • Across Period (Decreases)
     • Effective nuclear charge increases
   • Down the group (Increases)
     • Increase in quantum shell
   • Ionic Radius
     • Down the down (Increases)
       • Increase in quantum shell
         • Cation radius < its atomic radius
           • lose electrons; nuclear charge is constant thus stronger force of attraction
         • Anion radius > its atomic radius
           • gain in electrons; extent of repulsion is greater thus weaker force of attraction
     • Across Period (Decreases)
       • nuclear charge increases
       • note: from Si4+ to P3-, there's a sharp increase due to anions having one more quantum shell
     • Ionisation Energy
       • Write down the configuration
         • Distance from nucleus
         • Inter-electron repulsion
       • Across Period: Effective nuclear charge
       • Down the group: Distance from nucleus
       • Electronegativity
         • Across Period: (Increases)
           • Effective nuclear charge
         • Down the group: (Decreases)
           • Distance from nucleus
         • Melting Point
           • Increases around a period until a maximum is reached at group IV (giant molecular structure) and then decreases across the period
           • Electrical Conducitvity
             • Increases through the metals and decreases through the metalloids and non-metals