Group 1 elements (alkali metals) and Group 17 elements (halogens) differ in their valence electrons, leading to distinct reactivities; Group 1 are highly reactive metals, while Group 17 are highly reactive nonmetals. Group 2 elements (alkaline earth metals) like 24Mg and Ca have two electrons in their outer shell, with differences in reactivity and metallic character increasing as you move down the group.
When comparing the properties of elements in Group 1 and Group 17, it's crucial to recognize their position in the periodic table and their respective characteristics. Group 1 elements, known as alkali metals, have a single electron in their outermost energy level, leading to similar chemical behaviors such as high reactivity with water and forming strong bases (alkalis). In contrast, Group 17 elements, called halogens, have seven electrons in their valence shell, making them very reactive as well but in a different way as they tend to gain an electron to form salts.
When it comes to Group 2 elements, known as the alkaline earth metals, they have two electrons in the outer shell and are also metallic with similar properties such as higher melting points compared to Group 1. Meanwhile, the halogens in Group 17 are nonmetals with properties like high electronegativity and diatomic molecular forms.
For the specific comparison between 24Mg and Ca (Calcium), although both are alkaline earth metals, we would expect Ca, being further down the group, to have a lower first ionization energy than Mg due to the increased atomic radius. Calcium would also likely have a higher metallic character and be more reactive due to its larger atomic size and decreased ionization energy.