#"Chlorine"# lies in Group 17; it has 7 valence electrons, all of which can be involved in bonding.
#"Aluminum"# lies in Group 3; it has 3 valence electrons.
#"Sodium"# lies in Group 1; it has the 1 valence electron.
#"Sulfur"# lies in Group 16; it has 6 valence electrons.
#"Chlorine"# lies in Group 17; it has the 7 valence electrons.
Typically, metals, LOSE electrons to form positive ions; certainly sodium metal does this; as does aluminum to form #Al^(3+)# ions. And non-metals gain electrons to form negative ions. And thus chlorine accepts an electron, i.e. it is reduced, to form #Cl^-#:
#1/2Cl_2 + e^(-) rarr Cl^(-)#
And typically sulfur is reduced to form #"sulfide ions"#:
#S + 2e^(-) rarr S^(2-)#
On the other hand, both sulfur and chorine can be oxidized up to #VI+# and #VII+# oxidation states if they react with a more electronegative element, viz. oxygen:
#1/2Cl_2 + 4H_2O rarr ClO_4^(-) + 8H^(+) +7e^(-)#
#S + 4H_2O rarr SO_4^(2-) + 8H^(+) +6e^(-)#
Both mass and charge should be balanced in these equations. Well, is they?
