Predict the properties of other elements in Group VII, given information about the elements

🔬 The Periodic Table – Group VII (Halogens) Properties

What are Group VII Elements?

Group VII (also called the halogens) includes fluorine (F), chlorine (Cl), bromine (Br), iodine (I) and the synthetic astatine (At). They all have seven valence electrons, making them eager to gain one electron to complete their outer shell.

Key Properties of Halogens

  • High reactivity – they react with metals to form salts.

  • Electronegativity – fluorine is the most electronegative element.

  • State at room temperature – F and Cl are gases, Br is a liquid, I and At are solids.

  • Colour – gases are colourless, liquids are yellowish, solids are dark.

  • Oxidation states – common +1, +3, +5, +7; the most stable is –1 (as halide ions).

Predicting Properties of Other Group VII Elements

  1. Look at electronegativity trend – it decreases down the group.

  2. Check state at room temperature – heavier halogens become liquids or solids.

  3. Consider oxidation states – heavier elements can access higher +5 and +7 states.

  4. Use analogy to water (H₂O) – halides form salts like NaCl, NaBr, NaI.

Example: Predicting Properties of Astatine (At)

Electronegativity – lower than iodine, so it’s less reactive.

State – solid at room temperature.

Oxidation states – can reach +7 (e.g., AtO₄⁻).

🔍 Exam tip: Remember that the heaviest halogen is the least reactive and often forms radioactive salts.

Table of Group VII Properties

ElementState @ 25 °CElectronegativityCommon Oxidation States
FGas3.98–1, +1
ClGas3.16–1, +1, +3, +5, +7
BrLiquid2.96–1, +1, +3, +5, +7
ISolid2.66–1, +1, +3, +5, +7
AtSolid≈2.2–1, +1, +3, +5, +7

Exam Tip Box

📚 Remember: For any halogen, the most stable oxidation state is –1 (as a halide ion). When predicting reactions, think of the halogen as a “greedy” element that wants to fill its outer shell. Use the trend of electronegativity and state to justify your predictions.

📝 Practice Question: Predict the product of the reaction between Br₂ and Na at 25 °C. (Answer: NaBr + NaBr₂ – the latter is unstable and decomposes).