Chapter 4: Problem 45
Give the oxidation numbers for the underlined atoms in the following molecules and ions: (a) \(\mathrm{ClF},(\mathrm{b}) \mathrm{IF}_{7}\) (c) \(\underline{\mathrm{C}} \mathrm{H}_{4}\) (d) \(\underline{\mathrm{C}}_{2} \mathrm{H}_{2}\) (e) \(\underline{\mathrm{C}}_{2} \mathrm{H}_{4}\) (f) \(\mathrm{K}_{2} \mathrm{Cr} \mathrm{O}_{4},(\mathrm{~g}) \mathrm{K}_{2} \mathrm{Cr}_{2} \mathrm{O}_{7}\) (h) \(\mathrm{KMnO}_{4}\), (i) \(\mathrm{NaHCO}_{3},(\mathrm{j}) \mathrm{Li}_{2},(\mathrm{k}) \mathrm{NaIO}_{3},\) (I) \(\mathrm{KO}_{2}\), \((\mathrm{m}) \mathrm{PF}_{6}^{-},(\mathrm{n}) \mathrm{K} \mathrm{AuCl}_{4}\)
Short Answer
Expert verified
(a) +1, (b) +7, (c) -4, (d) -1, (e) -2, (f) +6, (g) +6, (h) +7, (i) +4, (j) 0, (k) +5, (l) -1/2, (m) +5, (n) +3.
Step by step solution
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Oxidation States
Oxidation states, also known as oxidation numbers, are essential in understanding how electrons interact within a chemical compound. They allow us to determine the electron distribution among atoms, indicating which atoms might lose or gain electrons during a chemical reaction.
The oxidation state of an element in a compound is a hypothetical charge, assuming that all bonds are ionic. For instance, in the molecule ClF, fluorine, being the most electronegative element, is assigned an oxidation state of -1. Consequently, chlorine's oxidation state becomes +1, so the compound remains neutral. Usually, group 1 elements have an oxidation state of +1, while group 2 elements have +2.
In molecules,
The oxidation state of an element in a compound is a hypothetical charge, assuming that all bonds are ionic. For instance, in the molecule ClF, fluorine, being the most electronegative element, is assigned an oxidation state of -1. Consequently, chlorine's oxidation state becomes +1, so the compound remains neutral. Usually, group 1 elements have an oxidation state of +1, while group 2 elements have +2.
In molecules,
- The oxidation state of oxygen is typically -2, except in peroxides or superoxides where it is -1 or -1/2, respectively.
- Hydrogen has an oxidation state of +1 when paired with more electronegative elements, like carbon or oxygen, but behaves differently in metal hydrides.
Chemical Compounds
Chemical compounds are formed when two or more atoms are chemically bonded together, resulting in a substance with unique properties differing from the individual elements involved.
Compounds can be characterized by their oxidation states, which reveal how electrons are shared or transferred among atoms within a compound. For instance, sodium chloride (NaCl) consists of sodium (Na) with an oxidation state of +1 and chlorine (Cl), having -1.
Each element in a compound influences the overall charge. For example, in sodium iodate (NaIO extsubscript{3}), the oxidation state of sodium is +1, iodine is +5, and each oxygen is -2. Together, they balance out to form a stable compound with a neutral charge.
The understanding of these compounds offers vital insight into chemical behavior, reactions, and properties, which is crucial for tasks such as synthesis and chemical analysis. This formalizes the connection between chemical composition and function, making it impactful in areas ranging from industry to biology.
Compounds can be characterized by their oxidation states, which reveal how electrons are shared or transferred among atoms within a compound. For instance, sodium chloride (NaCl) consists of sodium (Na) with an oxidation state of +1 and chlorine (Cl), having -1.
Each element in a compound influences the overall charge. For example, in sodium iodate (NaIO extsubscript{3}), the oxidation state of sodium is +1, iodine is +5, and each oxygen is -2. Together, they balance out to form a stable compound with a neutral charge.
The understanding of these compounds offers vital insight into chemical behavior, reactions, and properties, which is crucial for tasks such as synthesis and chemical analysis. This formalizes the connection between chemical composition and function, making it impactful in areas ranging from industry to biology.
Electronegativity
Electronegativity refers to the ability of an atom in a molecule to attract electrons towards itself. This concept is pivotal in determining how atoms will interact, especially in deciding oxidation states.
A highly electronegative atom, such as fluorine, will attract electrons strongly towards itself. This means that in compounds like IF extsubscript{7}, fluorine takes electrons away from iodine, assigning itself an oxidation state of -1, leaving iodine with +7.
Generally, electronegativity increases across a period from left to right and decreases down a group in the periodic table. Elements with high electronegativity often pull electrons towards them, thus commonly exhibiting negative oxidation states in compounds.
A highly electronegative atom, such as fluorine, will attract electrons strongly towards itself. This means that in compounds like IF extsubscript{7}, fluorine takes electrons away from iodine, assigning itself an oxidation state of -1, leaving iodine with +7.
Generally, electronegativity increases across a period from left to right and decreases down a group in the periodic table. Elements with high electronegativity often pull electrons towards them, thus commonly exhibiting negative oxidation states in compounds.
- Fluorine is the most electronegative element and always has an oxidation state of -1 in its compounds.
- Oxygen is also highly electronegative, usually exhibiting an oxidation state of -2.
- In contrast, hydrogen, which is less electronegative, tends to have an oxidation state of +1.
Neutral Molecules
Neutral molecules are compounds with no net charge. This is achieved when all the positive and negative charges within a molecule are balanced.
In the context of oxidation states, the algebraic sum of all the oxidation numbers in a neutral molecule must be zero. For instance, in methane (CH extsubscript{4}), carbon has an oxidation state of -4, while each hydrogen is +1, leading to a sum of -4 + 4 = 0, which confirms its neutrality.
Neutrality is observed in many molecular compounds, such as PF extsubscript{6} extsuperscript{-}. Here, the overall charge of -1 (due to the extra electron) is balanced by the phosphorus atom's +5 charge and the -1 from each of the six fluorine atoms.
In the context of oxidation states, the algebraic sum of all the oxidation numbers in a neutral molecule must be zero. For instance, in methane (CH extsubscript{4}), carbon has an oxidation state of -4, while each hydrogen is +1, leading to a sum of -4 + 4 = 0, which confirms its neutrality.
Neutrality is observed in many molecular compounds, such as PF extsubscript{6} extsuperscript{-}. Here, the overall charge of -1 (due to the extra electron) is balanced by the phosphorus atom's +5 charge and the -1 from each of the six fluorine atoms.
- In such compounds, ensuring charge balance is essential to predict the chemical behavior and reactivity.
- Neutrality also affects solubility and conductivity, pivotal for understanding their applications in real-world scenarios.
- Particular attention must be paid to ensure the correct electron count, especially in complex ions and molecules.
