To which group in the periodic table does element M belong?

Question

A certain element M is a main group metal that reacts with chlorine to give a compound with the chemical formula MCl2 and oxygen to give the compound MO. To which group in the periodic table does element M belong?

Answer 1

The formula of this compound suggests that M is a +2 cation.  This is determine by considering the formulas of the compounds given.   It forms a neutral compound with the formula MCl_2. Cl is a -1 anion.  In order to form a neutral compound with M, we have a determine the charge of M.

 

  M  +  2 Cl- = 0

  M   +  2 (-1) =0

        M=+2

 

It also forms a neutral compound with the formula MO. O is a -2 anion. In order to form a neutral compound with M, we have a determine the charge of M.

 

   M + 1 O^-2 = 0 
   M + (-2)   = 0   

   M = +2

 

Now, determine which metals on the periodic table form +2 cations (hint: column 1, alkali metals form +1 cations)