Periodicity -Acid Base Character

Acid-base character of oxides
Base behaviour : Na2O, MgO
Na2O(s) + 2HCl(aq) → 2NaCl(aq) + H2O(l)
MgO(s) + 2HCl(aq)→MgCl2(aq) + H2O(l)

Amphoteric behaviour Al2O3
Al2O3(s) + 6HCl(aq) → 2AlCl3 + 3H2O(l)
Al2O3(s) + 2NaOH(aq) +3H2O(l) → 2NaAl(OH)4(aq) sodium aluminate

Acid behaviour : SiO2, P4O10, P4O6
SiO2 + 2NaOH(aq) → Na2SiO3(aq) + H2O
P4O10 + 12NaOH → 4Na3PO4 + 6H2O
P4O6 + 12NaOH → 4Na3PO3 + 6H2O

Formulae of chlorides and reactions with water

NaCl + aq →Na+(aq) + Cl-(aq) dissolves to form neutral solution , pH = 7

MgCl2 + aq → Mg2+(aq) + 2Cl-(aq) dissolves with slight hydrolysis to form slightly acidic solution , pH = 6.5

AlCl3 + 6H2O(l) → [Al(H2O)6]3+(aq) + 3Cl-(aq) dissolves with hydrolysis to form acidic solution
[Al(H2O)6]3+(aq) →[Al(OH)(H2O)5]2+(aq) + H+(aq) , pH = 3

SiCl4 + 2H2O→SiO2 + 4HCl , pH = 2

PCl3 + 3H2O → H3PO3 + 3HCl, pH = 2

PCl5 + H2O → POCl3 + 2HCl, pH =2