Answer:
Magnesium (Mg)
Explanation:
The reation between beryllium (Be) and chlorine (Cl2):
[tex]Be + Cl_2 \longrightarrow BeCl_2[/tex]
The elements that may form a compound with a similar formula of the BeCl2 are some of the other members of the Group II of the periodic table.
One example of this is the reaction of chlorine with magnesium:
[tex]Mg + Cl_2 \longrightarrow MgCl_2[/tex]