in period 3, Na, Mg and Al are metals, so conduct electricity and react with acids
in period 3, Si is a semi-metal, so conducts electricity to some extent
in period 3, P, S and Cl are non-metals, so do not conduct electricity
in period 3, Ar is a noble gas, so is chemically unreactive
the reactions of the elements of period 3 are redox because all elements start with oxidation states of zero, and after reacting have a positive or negative oxidation state
Na and Mg are the only metal elements in period 3 that react with cold water
observations when Na reacts with water:
metal floats on the surface
rapid effervescence
metal melts due to heat emitted
equation for Na reacting with water:
2Na + 2H2O -> 2NaOH + H2
when Na reacts with water, a strongly alkaline solution of sodium hydroxide is formed, with a pH of 13-14
observation when Mg reacts with water:
very little effervescence
equation for Mg reacting with water:
Mg + 2H2O -> Mg(OH)2 + H2
when Mg reacts with water, a slightly alkaline solution is formed, with a pH of 10
the rate of the reaction of Mg with water can be increased by using heated magnesium and steam
observation when Mg reacts with steam:
bright white flame
equation for Mg reacting with steam:
Mg + H2O -> MgO + H2
Cl is the only non-metal element in period 3 that reacts with water
the oxides of the period 3 elements can be prepared by reacting them directly with oxygen
equation for production of sodium oxide:
2Na + 1/2(O2) -> Na2O
equation for production of magnesium oxide:
2Mg + O2 -> 2MgO
equation for production of aluminium oxide:
4Al + 3O2 -> 2Al2O3
equation for production of silicon dioxide:
Si + O2 -> SiO2
equation for production of phosphorus pentoxide:
4P + 5O2 -> P4O10
equation for production of sulfur dioxide and sulfur trioxide:
S + O2 -> SO2 + small amount of SO3
the oxides of Na, Mg and Al are made up of a metal and a non-metal so are compounds with ionic bonding, forming a giant ionic lattice, this gives them high melting points
the oxide of Al has some covalent character as well as being ionic because the ion is very small and positive so can closely approach the oxygen atom and distort its electron cloud
the oxide of Si has a macromolecular structure, so forms a giant covalent lattice, this gives it a high melting point
the oxides of P and S have simple molecular structure, so are made up of separate covalently bonded molecules, this gives them relatively low melting points as they only have van der Waals and dipole-dipole intermolecular forces
the order of melting points of period 3 oxides is:
MgO > Al2O3 > SiO2 > Na2O > P4O10 > SO3 > SO2
MgO and Na2O are both bases, so can react with water to make an alkaline solution
equation for magnesium oxide reacting with water:
MgO + H2O -> Mg(OH)2
equation for sodium oxide reacting with water:
Na2O + H2O -> 2NaOH
sodium oxide reacting with water produces a strongly alkaline solution of sodium hydroxide with a pH of 14
magnesium oxide reacting with water produces a slightly alkaline solution of magnesium hydroxide with a pH of 9
Al2O3 and SiO2 are both insoluble in water
P4O10, SO2 and SO3 are acidic, so react with water to make an acidic solution
equation for phosphorus pentoxide reacting with water:
P4O10 + 6H2O -> 4H3PO4
phosphorus pentoxide reacting with water produces an acidic solution of phosphoric acid with a pH of -1 to +1
equation for sulfur dioxide reacting with water:
SO2 + H2O -> H2SO3
sulfur dioxide reacting with water produces an acidic solution of sulfurous acid with a pH of 1