Halogens are group 7 compounds on the periodic table. They have 7 valence electrons, therefore they are very reactive since they tend to form bonds with group 1 elements to fill their energy level with 8 electrons to comply with the octet rule. The halogens tend to have a higher binding energy as one descends vertically in the periodic table, which implies that as the halogen element is larger, its reactivity is lower, therefore the two elements more reagents in this group are fluorine and chlorine.
Halogens differ from noble gases by their reactivity, since halogens are very reactive while noble gases are not. With metals they differ by their conductivity, metals have good conductivity while halogens not so much
In summary, we have:
a. What is the group number? VII or 7 group
b. Are these nonmetals reactive? Are very reactive
c. Name the two most reactive elements in this group? fluorine and chlorine
d. What distinguishes this group from other groups? Differ from noble gases by their reactivity. With metals they differ by their conductivity