8.7
Halogens
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Q1: Why are halogens considered highly reactive elements?
Halogens have seven valence electrons and are one electron short of attaining their nearest noble gas configuration. This electron deficit creates a strong tendency to gain one additional electron to complete their octet, making them highly reactive and powerful oxidizing agents. Fluorine is the most potent oxidizing agent amongst halogens, while iodine is the least reactive.
Q2: What are the physical states of halogens at room temperature?
Halogens exist as diatomic molecules with varying physical states at room temperature. Fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid. Astatine, the fifth halogen, is a rare and highly radioactive solid with limited known properties due to its short half-life.
Q3: How do atomic radii and melting points change across the halogen group?
Atomic radii increase with increasing atomic number moving down Group 17, from fluorine to iodine. Melting points and boiling points show an upward trend from fluorine to iodine. In contrast, periodic properties like electronegativity and reactivity decrease down the group as atomic size increases.
Q4: What happens when halogens react with metals?
Halogens react with most metals to yield metal halides, which are typically ionic compounds. For example, chlorine reacts with sodium to produce sodium chloride, and with iron to give iron chloride. These reactions occur because halogens gain the electron needed to complete their valence shell.
Q5: What are hydrogen halides and how do they form?
Halogens react with hydrogen to form polar covalent compounds called hydrogen halides. These compounds often dissolve in water to form hydrohalic acids. Hydrofluoric acid is the weakest haloacid produced from this reaction, while other hydrogen halides form stronger acids in aqueous solution.
Q6: What are interhalogen compounds and how are they formed?
Interhalogen compounds are binary covalent compounds formed when halogens react with each other. They follow the general molecular formula ABn, where A is the halogen with the higher atomic number and n is an odd number. Examples include bromine trifluoride, ICl, IBr, and BrF.
Q7: How does fluorine's reactivity with water differ from chlorine's?
Fluorine reacts highly exothermically with water, producing hydrogen fluoride—a strong acid—and oxygen. Chlorine reacts more slowly, producing hydrochloric acid and hypochlorous acid, a strong oxidizing agent. These differences reflect fluorine's greater reactivity and stronger tendency to gain electrons compared to chlorine.