The oxidation number of an element in a compound is evaluated on the b...
as oxygen is more electronegative than Cl,Br and I. So they have positive oxidation state.
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The oxidation number of an element in a compound is evaluated on the b...
Explanation:
Oxidation number or state is a concept used to describe the degree of oxidation (loss of electrons) of an atom in a compound. The oxidation number of an element in a compound is evaluated on the basis of certain rules. Let's discuss each rule one by one and find out which one is not correct.
a) The algebraic sum of all the oxidation numbers in a compound is zero: This rule is correct. The sum of oxidation numbers of all the atoms in a neutral compound is always zero. For example, in H2O, the oxidation number of hydrogen is +1 and the oxidation number of oxygen is -2. So, the sum of oxidation numbers is (2*+1) + (-2) = 0.
b) In all its compounds, the oxidation number of fluorine is 1: This rule is not correct. The oxidation number of fluorine in its compounds is always -1, except in a few highly electronegative compounds where it exhibits positive oxidation states. For example, in HF, the oxidation number of fluorine is -1, while in OF2, the oxidation number of fluorine is +2.
c) An element in the free or the uncombined state bears oxidation number zero: This rule is correct. The elements in their elemental form have zero oxidation state. For example, the oxidation state of oxygen in O2 is zero and the oxidation state of iron in Fe is also zero.
d) The oxidation number of hydrogen is always 1: This rule is not correct. The oxidation number of hydrogen can vary from -1 to +1, depending on the compound it is present in. For example, in H2O, the oxidation number of hydrogen is +1, while in NaH, the oxidation number of hydrogen is -1.
Therefore, the correct answer is option D.
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