Halogens (Group 17): Physical Properties and Reactions

Question-and-answer flashcards covering the physical properties, chemical reactivity, and notable reactions of halogens (Group 17) as described in the notes.

What are the states of matter for halogens at room temperature?

F2 and Cl2 are gases, Br2 is a liquid, and I2 and At2 are solids.

How do halogen colors change down the group?

Colors become darker: F2 pale yellow gas, Cl2 greenish-yellow gas, Br2 reddish-brown liquid, I2 grey-black solid with purple vapor.

Why do melting and boiling points increase down the group?

Because van der Waals' (London dispersion) forces strengthen as the number of electrons increases, raising MP and BP.

What happens to halogen volatility as you move down the group?

Volatility decreases down the group due to stronger intermolecular forces and higher boiling points.

How does halogen reactivity change down the group, and why?

Reactivity decreases down the group because the atoms get larger, outer electrons are farther from the nucleus and more shielded, making electron gain harder.

What is the role of halogens as oxidizing agents, and how does this change down the group?

Halogens are oxidizing agents (they accept electrons). Their oxidizing power decreases down the group; a more reactive halogen can displace a less reactive one from a halide solution.

What happens when halogens react with metals?

They form metal halides via redox reactions; halogen is reduced and the metal is oxidized.

What are halide ions and their reducing behavior?

Halide ions F−, Cl−, Br−, I− can act as reducing agents; reducing power increases down the group (F− < Cl− < Br− < I−).

Describe the reaction of halide ions with concentrated sulfuric acid.

Cl− cannot reduce H2SO4 (produces HCl); Br− reduces it to SO2; I− is the strongest reducing agent and can reduce to sulfur or H2S.

What is chlorine’s disproportionation reaction with cold, dilute alkali?

Chlorine can be oxidized and reduced to form chloride (Cl−) and chlorate(I) (ClO−) ions.

How is chlorine used in water purification and what species forms?

Chlorine reacts with water to form hypochlorous acid (HClO), a sterilizing agent.