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General Chemistry Principles, Patterns, and Applications, 2011

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Note the Pattern<br />

Both the acid strength <strong>and</strong> the oxidizing power of the halogen oxoacids decrease down the group.<br />

The halogens react with one another to produce interhalogen compounds, such as ICl3, BrF5, <strong>and</strong> IF7. In<br />

all cases, the heavier halogen, which has the lower electronegativity, is the central atom. The maximum<br />

oxidation state <strong>and</strong> the number of terminal halogens increase smoothly as the ionization energy of the<br />

central halogen decreases <strong>and</strong> the electronegativity of the terminal halogen increases. Thus depending on<br />

conditions, iodine reacts with the other halogens to form IFn (n = 1–7), ICl or ICl3, or IBr, whereas<br />

bromine reacts with fluorine to form only BrF, BrF3, <strong>and</strong> BrF5 but not BrF7. The interhalogen compounds<br />

are among the most powerful Lewis acids known, with a strong tendency to react with halide ions to give<br />

complexes with higher coordination numbers, such as the IF8 − ion:<br />

Equation 22.45<br />

IF 7 (l) + KF(s) → KIF 8 (s)<br />

All group 17 elements form compounds in odd oxidation states (−1, +1, +3, +5, +7). The interhalogen<br />

compounds are also potent oxidants <strong>and</strong> strong fluorinating agents; contact with organic materials or<br />

water can result in an explosion.<br />

Note the Pattern<br />

All group 17 elements form compounds in odd oxidation states (−1, +1, +3, +5, +7), but the importance of<br />

the higher oxidation states generally decreases down the group.<br />

E X A M P L E 9<br />

For each reaction, explain why the given products form.<br />

a. ClF 3(g) + Cl 2(g) → 3ClF(g)<br />

b. 2KI(s) + 3H 2SO 4(aq) → I 2(aq) + SO 2(g) + 2KHSO 4(aq) + 2H 2O(l)<br />

c. Pb(s) + 2BrF 3(l) → PbF 4(s) + 2BrF(g)<br />

Given: balanced chemical equations<br />

Asked for: why the given products form<br />

Strategy:<br />

Classify the type of reaction. Using periodic trends in atomic properties, thermodynamics, <strong>and</strong> kinetics, explain<br />

why the observed reaction products form.<br />

Solution:<br />

Saylor URL: http://www.saylor.org/books<br />

Saylor.org<br />

2057

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