2.2 Group 7 (Halogens)Edexcel IGCSE Chemistry: Flashcards

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What colour and state is chlorine at room temperature?

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What colour and state is chlorine at room temperature?: A pale green (yellow-green) gas.
What colour and state is bromine at room temperature?: A red-brown liquid.
What colour and state is iodine at room temperature?: A grey-black solid, which sublimes to a purple vapour on heating.
How do melting and boiling points change down Group 7?: They increase down the group, as intermolecular forces get stronger with increasing relative molecular mass.
How does reactivity change down Group 7?: Reactivity decreases down the group.
Define a displacement reaction.: A reaction in which a more reactive element takes the place of a less reactive element in a compound.
What happens when chlorine is added to potassium bromide solution?: Chlorine displaces bromine: Cl2 + 2KBr → 2KCl + Br2; the solution turns orange.
Does bromine displace chlorine from potassium chloride solution?: No — bromine is less reactive than chlorine, so no reaction occurs.
Why does reactivity decrease down Group 7?: Atoms get larger down the group, so the outer shell is further from the nucleus and more shielded, making it harder for the nucleus to attract and gain an extra electron.
How do halogen atoms react to form ions?: By gaining one electron each to form a 1- halide ion with a full outer shell.
Predict the state of fluorine at room temperature.: A gas (even paler and more reactive than chlorine, as it is above chlorine in the group).
What is a halide?: An ion or compound formed from a halogen, e.g. chloride (Cl-), bromide (Br-), iodide (I-).
What colour change is seen when chlorine displaces iodine from potassium iodide solution?: The colourless solution turns brown as iodine is formed.
Why do melting and boiling points increase down Group 7?: Molecules get larger (more electrons) going down the group, so intermolecular forces between molecules get stronger, needing more energy to overcome.