Assign oxidation numbers to each element in (a) nitrogen oxide (b) ammonia (c) potassium peroxide (d) chlorate ion \(\left(\mathrm{ClO}_{3}^{-}\right)\)

Understanding chemical formulas is foundational in chemistry. A chemical formula is a way of presenting information about the chemical proportions of atoms that constitute a particular chemical compound or molecule, using chemical element symbols and numerical subscripts. For example, nitrogen oxide is expressed as NO, ammonia as NH₃, potassium peroxide as K₂O₂, and the chlorate ion as ClO₃^-.

Each element in a compound has a fixed proportion, providing insights into the molecular structure and stoichiometry, which is the quantitative relationship between reactants and products in a chemical reaction. Understanding the composition helps to predict the properties and behavior of the material, like its reactivity or state of matter.

The concept of oxidation state, or oxidation number, is a fundamental principle used to describe the degree of oxidation of an element in a chemical compound. It represents the hypothetical charge an atom would have if all bonds to atoms of different elements were completely ionic. It is essential for balancing redox reactions and determining electron transfer.

The oxidation number is usually an integer, positive or negative, suggesting how many electrons an atom has lost, gained, or shared in forming a chemical bond. For instance, the nitrogen in nitrogen oxide (NO) typically has an oxidation number of -3 but in NO, it is +2 to balance the -2 charge typically seen for oxygen. This assignment respects the principle that the sum of the oxidation states in a neutral compound is zero, or equal to the net charge of a polyatomic ion.

A polyatomic ion is a charged species composed of two or more atoms covalently bonded together, or of a metal complex that acts as a single unit. The charge on a polyatomic ion is not a result of an excess or deficit of electrons, but rather the result of the compound or complex having an overall electron count that doesn't match the total valence electron count of the constituent atoms.

For instance, the chlorate ion, ClO₃^-, is a polyatomic ion. It has more electrons than protons, giving it a net negative charge (-1). Assigning oxidation states helps in understanding the distribution of electrons among the atoms within a polyatomic ion. In chlorate, chlorine (Cl) has an oxidation state of +5, while oxygen has a -2 oxidation state.

A neutral compound is a chemical species that bears no net charge, meaning the total of all oxidation numbers of the atoms in the compound should add up to zero. The principle of electroneutrality holds that the sum of the positive charges should equal the sum of the negative charges.

Examples of neutral compounds are nitrogen oxide (NO) and ammonia (NH₃). In NH₃, for example, the nitrogen atom has an oxidation number of -3, and each hydrogen atom has an oxidation number of +1. When combined, the total oxidation number sums up to zero, indicating that ammonia is a neutral compound. Acknowledging this property enhances the understanding of chemical bonding and molecular stability.