Period 3

Atomic Radius

• Decrease across period, number of shells remain the same, atomic number

• Nuclear charge increases across the period, greater attraction

• Except Al because easily loose e^– in p-block 

electronegativity and 1st IE

• both increase

• NC increase

• stronger attraction

Melting and Boiling Point

• Na to Al metallic bonding

• Si covalent macromolecular

• P to Cl simple molecular

Period 3 + Oxygen

gives oxide

Na yellow flame

Mg white flame

Al white flame

P white flame

S blue flame

reactions with chlorine

metals give white solid

and chloride

reaction with water

Si, P and S don’t react

NaOH

Mg(OH)2 or MgO

Cl gives HClO and HCl

Period 3 Oxides reaction with water

Na and Mg gives OH

P4O10 gives H3PO4

SO2 H2SO3

SO3 H2SO4

Chlorides in water

Na and Mg dissolves to give neutral solution

Al amphotric

SiCl4 ⟶ SiO2 + HCl

PCl5 ⟶ H3PO4 + HCl