Which of the following statements about Group VII elements is correct?

Analyze the question: Group VII elements are the halogens (F, Cl, Br, I, At). We need the one true statement about them.

Concept: Halogens have 7 valence electrons and tend to gain one electron to form X⁻. This makes them oxidizing agents. Going down the group, atomic size increases, the nucleus attracts the incoming electron less strongly, so the tendency to gain electrons falls.

Checking each option:

• A. Same physical state – False. At room temperature, fluorine and chlorine are gases, bromine is a liquid, and iodine is a solid.
• B. Strong reducing agents – False. Halogens are strong oxidizing agents because they readily gain electrons. (Their halide ions, such as I⁻, are the reducing agents.)
• C. Reactivity decreases down the group – True. F₂ is the most reactive, then Cl₂, Br₂, I₂. A more reactive halogen displaces a less reactive one from its salt solution, e.g. Cl₂ + 2KBr → 2KCl + Br₂.
• D. Monoatomic molecules – False. Halogens exist as diatomic molecules (F₂, Cl₂, Br₂, I₂). Monoatomic gases are the noble gases (Group VIII/0).

Exam tip: Remember the contrast between the two ends of the periodic table. For Group I metals, reactivity increases down the group. For Group VII halogens, reactivity decreases down the group. A quick way to recall the halogen states is "Gas, Gas, Liquid, Solid" for F, Cl, Br, I.