properties of period 3 elements and their oxides

• sodium with cold water

  2Na (s) + 2H2O (l) → 2NaOH (aq) + H2 (g)

  -vigorous

  -exothermic

  -sodium floats on surface fizzing and melting due to heat produced

  -NaOH produced pH 13-14
• magnesium with cold water

  Mg (s) + 2H2O (l) → Mg(OH)2 (aq) + H2 (g)

  -extremely slow

  -Mg(OH)2 pH 10 - only partially soluble
• heated magnesium with steam

  Mg (s) + H2O (g) → MgO (s) + H2 (g)

  -much faster than with cold water

  -Mg burns with a bright white flame
• Na and Oxygen

  4Na(s) + O2(g) ---> 2Na2O(s)

  conditions: heated

  reaction: vigorous

  flame: bright yellow flame

  product: white solid

  product acid/base nature: basic
• Mg and oxygen

  2Mg(s) + O2(g) ---> 2MgO(s)

  conditions: heated

  reaction: vigorous

  flame: bright white flame

  product: white solid

  product acid/base nature: basic
• Al and oxygen

  4Al(s) + 3O2(g) ---> 2Al2O3(s)

  conditions: powdered Al

  reaction: fast

  flame: bright white flame

  product: white powder

  product acid/base nature: amphoteric
• Si and Oxygen

  Si(s) + O2(g) ---> SiO2(s)

  conditions: powdered Si, heated strongly

  reaction: slow

  flame: bright white sparkles

  product: white powder

  product acid/base nature: acidic
• P and oxygen

  4P(s) + 5O2(g) ---> P4O10(s)

  conditions: heated

  reaction: vigorous

  flame: yellow or white flame

  product: white clouds

  product acid/base nature: acidic
• S and oxygen

  S(s) + O2(g) ---> SO2(g)

  conditions: powdered S is heated

  reactions: gently

  flame: blue flame

  products: toxic fumes

  product acid/base nature: acidic
• sulfurs oxides

  -can form SO2 and SO3

  -formation of SO3 needs a catalyst and very high temperatures

  2S(s) + 3O2(g) ---> 2SO3(g)
• ionic oxides - melting points

  Na2O, MgO, Al2O3

  -ionic oxides because bonding exists between metal and non metals

  -giant lattice structures - high melting points

  -MgO - very high point due to bond strength - very high electronegativities between mg and o - atoms will strongly attract eachother
• giant covalent oxides - melting points

  SiO2

  -covalent because silicon and oxygen are non metals

  -extremely strong covalent bonds - high point
• simple covalent oxides - melting points

  P4O10, SO2,SO3

  -small molecules with weak intermolecular forces

  -SO2 and SO3 both gasses at room temp
• oxides of Na and Mg with water

  -oxides show purely ionic bonding

  -produce alkaline solns as O2- become OH-

  O2- (aq) + H2O (l) → 2OH- (aq)
• oxides of P ans S with water

  -oxides show purely covalent bonding

  -produce acidic solns - form an acid which donated H+ to water

  SO3 (g) + H2O (l) → H2SO4 (aq)
• non metal oxides with water

  -Oxides of phosphorus and sulfur are simple covalent molecules

  -They will react with water to produce acidic solutions
• uses of MgO

  used in indigestion remedies by neutralising the excess acid in the stomach