Question

Assign oxidation states to all of the atoms in each of the following: a. \(\mathrm{P}$$_{4}\) b. \(\mathrm{HClO}\) c. \(\mathrm{CH}_{4}\) d. \(\mathrm{H}_{2} \mathrm{PO}_{4}^{-}\)

Short answer

In the given compounds, the oxidation states of the atoms are as follows: a. \(P_{4}\): \(P = 0\) b. \(HClO\): \(H = +1\), \(Cl = +1\), \(O = -2\) c. \(CH_{4}\): \(H = +1\), \(C = -4\) d. \(H_{2}PO_{4}^{-}\): \(H = +1\), \(P = +5\), \(O = -2\)

Step-by-step solution

a. \(P_{4}\)

The compound consists of four phosphorus (P) atoms bonded together. Since all the phosphorus atoms are the same element, the oxidation state for each P is zero. Oxidation states: \(P = 0\)

b. \(HClO\)

This compound consists of three atoms: hydrogen (H), chlorine (Cl), and oxygen (O). We can use the rules mentioned above to assign oxidation states. Hydrogen has an oxidation state of +1, oxygen usually has an oxidation state of -2, and chlorine will have the remaining oxidation state. Oxidation states: \(H = +1\), \(O = -2\) For Cl: (+1) + (? ox. state of Cl) + (-2) = 0 Hence, the oxidation states are: \(H = +1\), \(Cl = +1\), and \(O = -2\).

c. \(CH_{4}\)

This compound consists of one carbon (C) atom bonded to four hydrogen (H) atoms. Hydrogen has an oxidation state of +1, so the total oxidation states of the four hydrogen atoms are +4. Since the molecule is neutral, the oxidation state of carbon must be -4 to balance the overall oxidation states. Oxidation states: \(H = +1\), \(C = -4\)

d. \(H_{2}PO_{4}^{-}\)

This ion consists of two hydrogen (H) atoms, one phosphorous (P) atom, and four oxygen (O) atoms. Hydrogen has an oxidation state of +1, oxygen usually has an oxidation state of -2. Since the ion has a net charge of -1, we can find the oxidation state of phosphorus based on the other known oxidation states. Oxidation states: \(H = +1\), \(O = -2\) For P: 2(+1) + (? ox. state of P) + 4(-2) = -1 Summing up the four oxidation states (-1 = 1*2 + P + -2*4), we get the oxidation state of phosphorous as +5. Hence, the oxidation states are: \(H = +1\), \(P = +5\), and \(O = -2\).

Key concepts

Chemical Compounds

Chemical compounds are formed when two or more elements combine to create a new substance with unique properties. These compounds can be either ionic, where electrons are transferred between atoms, or covalent, where electrons are shared. The properties of a compound differ significantly from those of its individual elements.
For example, water (H₂O) is a chemical compound made of hydrogen and oxygen, yet it exhibits very different properties from those two gases. When studying chemical compounds, identifying their molecular structure is crucial. This not only involves understanding the bonds within the molecule but also determining the oxidation state of each element within the compound. The oxidation state is a concept that allows chemists to keep track of electron transfers. It is fundamental in understanding redox reactions and predicting the behavior of chemical compounds during reactions.

Atomic Structure

Every atom consists of a nucleus surrounded by electrons, which are arranged in specific orbits or energy levels. Atoms of different elements have varying numbers of protons, neutrons, and electrons, determining their specific properties and chemical behavior. Electrons play a critical role in chemical reactions, as they are involved in the formation of chemical bonds.
The outermost electrons, known as valence electrons, are the ones primarily involved in bonding and chemical reactions. The concept of valence assists in determining the oxidation states of atoms in a compound. Each element has a typical oxidation state it often exhibits based on its atomic structure. Understanding atomic structure helps predict how atoms will interact to form compounds, including whether they will gain, lose, or share electrons during reactions.

Redox Reactions

Redox reactions, short for reduction-oxidation reactions, involve a transfer of electrons between chemical species. These reactions are significant in numerous chemical processes, from energy production in biological systems to the corrosion of metals.
In a redox reaction, one substance undergoes oxidation (loses electrons) while another undergoes reduction (gains electrons). Assigning oxidation states is crucial in identifying which species are oxidized and which are reduced. For example, in the reaction of hydrogen gas with chlorine gas to form hydrochloric acid, hydrogen is oxidized (its oxidation state increases from 0 to +1), while chlorine is reduced (its oxidation state decreases from 0 to -1). Understanding oxidation and reduction helps predict the outcomes of chemical reactions, explain changes in energy, and assess the environmental impacts of chemical processes.