Question

Discuss briefly the properties of group 17 elements (halogen family).

Answer 1

1. Group 17 elements include fluorine (F), chlorine (Cl), bromine (Br), iodine (I), and astatine (At). Collectively, they are called halogens.
2. Their electronic configuration is ns² np⁵, meaning they have 7 valence electrons and need 1 electron to complete their octet.
3. Atomic and ionic radii, density, and melting and boiling points increase down the group.
4. Ionisation energy and electronegativity decrease down the group.
5. They have the smallest atomic radius in their respective periods.
6. Halogens have high electron affinity, with chlorine having higher than fluorine.
7. Fluorine shows only the −1 oxidation state, but other halogens can show multiple states (−1, +1, +3, +5, +7).
8. All halogens have colour, which darkens down the group.
9. Reactivity decreases from fluorine to iodine.
10. They act as strong oxidising agents; their oxidising power decreases down the group.
11. They displace each other in salt solutions according to their reactivity order (e.g., fluorine displaces all others).
12. Fluorine forms the most ionic bonds in metal halides; ionic character decreases down the group.
13. Halogens form hydrogen halides with distinct properties like thermal stability and acidic strength, which vary down the group.