HI,
IF IT FORMS AN Oxide of the form XO,
KNOWIng that oxygen has a charge of -2,the element with which it is combined must have a charge of +2 to get a ratio of 1;1
so i think n i'm pretty sure that the answer is the group 2 elements(alkali earth metals) or it may also be a group 6(cuz the have two oxidation states the +2 and +4)
its up to u now,
goodluck
