Fig. 3.1 shows three of the halogens in the order they appear in Group VII. Fig. 3.1 (a) State how the reactivity of the elements changes going down Group V...
Question 1 Report
Fig. 3.1 shows three of the halogens in the order they appear in Group VII.
Fig. 3.1
(a) State how the reactivity of the elements changes going down Group VII. [1]
(b) Chlorine, bromine and iodine each react with hydrogen. Predict which of these three elements reacts most vigorously with hydrogen. [1]
(c) Fluorine is placed above chlorine in the group. Predict how the reactivity of fluorine compares with that of chlorine. [1]
(d) Describe, in terms of the size of the atoms, one reason why the elements become less reactive down the group. [2]
(e) State the colour and physical state of chlorine at room temperature. [2]
(f) Give the formula of a molecule of iodine. [1]
Answer Details
This question tests the trends down Group VII (the halogens). Going down the group the atoms get bigger, which makes them less reactive because they gain an electron less easily.
(a) Reactivity decreases going down Group VII [1].
(b) Of chlorine, bromine and iodine, the one highest in the group is the most reactive, so chlorine reacts most vigorously with hydrogen [1].
(c) Fluorine is above chlorine, so it is more reactive than chlorine [1].
(d) Going down the group the atoms get larger, so the outer shell is further from the nucleus [1]; the attraction on an incoming electron is weaker, so an outer electron is gained less easily and the element is less reactive [1].
(e) Chlorine is pale green / yellow-green [1] and is a gas [1] at room temperature.
(f) Iodine is diatomic, so a molecule is \( \text{I}_2 \) [1].
Exam tip: the halogen reactivity trend is the opposite of the metals in Group I; for halogens, reactivity is highest at the top (fluorine) because gaining an electron is easiest for the smallest atom.
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