Use lewis theory to determine the formula for the compound that forms from al and s.

Aluminium metal belongs to group 3 and it looses three electrons to form Al³⁺ ion. While, Sulfur belongs to group 6 and accepts 2 electrons to obtain noble gas configuration and forms S⁻².

The compound between Al and S is made in such a way that the nuber of Al atoms present in compound are multiplied by the charge number of sulfur (i.e -2) and number of Sulfur atoms are multiplied by the charge number on Aluminium (i.e +3),

So,
          Al  ×  2  = Al₂
And,
          S  ×  3  =  S₃

Result:
            The compound formed by Al and S is,

                                                Al₂S₃

Determine the  wavelength of light emitted when an electron  in an li2+ ion  makes a transition from an orbital with n  =  6 to an orbital with n  = 5.