Would compounds of the group 1 elements have the formula MX or MX2? M=Metal X= halide
Group 1 elements form MX and group 2 form MX₂.
The alkali metals (group one) in their elemental state are easily oxidized, losing one electron to form positive cations. Sodium becomes Na⁺. Chlorine can gain an electron and is reduced to Cl⁻. The equally balanced opposite charges are evidence why NaCl can form.
Group 2 elements lose two electrons, so calcium for example would ionize to be Ca²⁺. This would require two chlorine ions to balance out the charges. CaCl₂.