Final answer:
The 1:1 ratio in the ionic compounds formed by group 2 and group 16 elements is due to the fact that group 2 elements lose two electrons to become 2+ ions, while group 16 elements gain two electrons to become 2- ions,
Step-by-step explanation:
The ionic compounds that result from combining group 2 and group 16 elements have a 1:1 ratio because group 2 elements (like magnesium and calcium) have two electrons in their outermost shell, which they can lose to achieve a noble gas configuration. Group 16 elements (like oxygen and sulfur) need two additional electrons to complete their outer shell and reach a stable configuration as well.
When a group 2 element combines with a group 16 element, the group 2 element loses two electrons and becomes a 2+ ion, while the group 16 element gains two electrons and becomes a 2– ion. Therefore, one ion of each is needed to balance the charges, leading to a compound with a 1:1 stoichiometric ratio.
This stoichiometry is also consistent with the law of conservation of matter, which requires that the number of electrons lost by one species must equal the number of electrons gained by another, maintaining electrical neutrality in the resulting compound. Hence, the 1:1 ratio of cations to anions in the compounds formed by group 2 and group 16 elements is due to their need to balance electrical charges and the conservation of matter. This is similar to how group 1 elements form compounds in a 1:1 ratio with group 17 elements, balancing their respective 1+ and 1- charges.