Final answer:
Element M belongs to group 1 of the periodic table, known as the alkali metals group, as indicated by its compounds MX and M2S with iodine and sulfur respectively.
Step-by-step explanation:
To determine which group in the periodic table element M belongs to, we need to look at the chemical formulas of the compounds it forms with iodine and sulfur.
When M reacts with iodine, it forms a compound with the formula MX, which suggests that M forms a one-to-one ratio with iodine, a halogen. Since halogens are in group 17 and typically form -1 ions, element M must form a +1 ion to balance the charge, which indicates that M is in group 1 of the periodic table, also known as the alkali metals group.
The reaction with sulfur to form M2S, where M is a main-group metal and sulfur is from group 16 (the chalcogens), further supports this because sulfur typically forms a -2 ion (S2-), requiring two +1 ions from element M to balance the charge.