Final answer:
The correct match up for the element category and number of valence electrons is halogens with 7 valence electrons. Halogens are part of Group 7A, which typically have seven valence electrons, contributing to their high reactivity.
Step-by-step explanation:
The element category and the number of valence electrons that match up correctly are halogens with 7 valence electrons. This is because halogens belong to Group 7A of the periodic table, and elements in this group have seven valence electrons, not eight as option d suggests. They are known for their high reactivity due to their desire to gain one electron in order to achieve a stable octet. Option a (Nonmetals, 4 valence electrons) is not specific enough as nonmetals include multiple groups with varying numbers of valence electrons. Option b (Alkali metals, 2 valence electrons) is incorrect because alkali metals, which are found in Group 1 of the periodic table, have one valence electron, not two. Option c (Noble gases, 6 valence electrons) is also incorrect since noble gases, being in Group 8A (or Group 18 in some periodical table representations), have 8 valence electrons with filled outermost energy levels, thus they are stable and mostly unreactive.