Determine the oxidation numbers of all the elements in each...

Determine the oxidation numbers of all the elements in each of the following compounds. (Hint: Look at the ions present.) (a) $\mathrm{Hg}_{2}\left(\mathrm{ClO}_{4}\right)_{2}$ (b) $\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}$ (c) $\mathrm{CoSeO}_{4}$ (d) $\mathrm{Pb}(\mathrm{OH})_{2}$

Determine the oxidation numbers of all the elements in each of the following compounds. (Hint: Look at the ions present.)
(a) $\mathrm{Hg}_{2}\left(\mathrm{ClO}_{4}\right)_{2}$
(b) $\mathrm{Cr}_{2}\left(\mathrm{SO}_{4}\right)_{3}$
(c) $\mathrm{CoSeO}_{4}$
(d) $\mathrm{Pb}(\mathrm{OH})_{2}$

Key Concepts

Oxidation Numbers

Oxidation numbers (or oxidation states) are a bookkeeping tool used in chemistry to keep track of electron transfer in chemical reactions. They represent the hypothetical charges that atoms would have if all bonds were completely ionic, and are essential in balancing redox reactions and understanding electron flow in compounds.

Electroneutrality Principle

The electroneutrality principle states that the total sum of oxidation numbers in a neutral compound must be zero, while in a polyatomic ion it must equal the ion's net charge. This principle is used to determine unknown oxidation states by ensuring that the overall charge is balanced.

Rules for Assigning Oxidation States

There are standard rules for assigning oxidation numbers, such as oxygen typically being assigned -2 (with exceptions like peroxides), hydrogen usually +1 (except when bonded to metals in hydrides), and the fact that elements in their elemental form have an oxidation state of zero. These rules serve as guidelines when calculating unknown oxidation states in complex structures.

Polyatomic Ions

Polyatomic ions are charged species composed of several atoms covalently bonded together, whose total oxidation numbers add up to the ion's charge. Determining the oxidation states within polyatomic ions often involves using known oxidation states of common elements (like oxygen) and applying the electroneutrality principle to deduce the oxidation state of less obvious atoms.

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