Chlorine can exist in both positive and negative oxidation states. What is the maximum (a) positive and (b) negative oxidation number that chlorine can have? (c) Write the electron configuration for each of these states. (d) Explain how you arrived at these values.

Chemical bonding is a fundamental concept in chemistry that explains how atoms bind together to form molecules. At its core, it involves the interaction of electrons, particularly the valence electrons, which reside in the outermost shell of an atom. Chlorine, a member of Group 17 in the periodic table, is a halogen with seven valence electrons. Due to its electron configuration, chlorine has a high electronegativity, making it very effective at forming chemical bonds either by gaining an electron to achieve a full octet and a negative oxidation state or by sharing its electrons with other atoms, potentially leading to positive oxidation states.

To understand chlorine's oxidation states, we must consider its ability to either lose or share electrons when forming compounds. In the case of the maximum positive oxidation state, which is +7, chlorine participates in oxidation states where it is bonded to more electronegative elements such as oxygen or fluorine. In compounds like perchlorates (ClO4−), chlorine shares all of its seven valence electrons, resulting in the +7 state. Conversely, when chlorine achieves its most stable negative oxidation state of -1, as in sodium chloride (NaCl), it has gained one electron, achieving a noble gas electron configuration similar to argon, showcasing the completion of its octet.

The electron configuration of an atom describes the arrangement of electrons in its atomic orbitals and is pivotal in predicting the chemical and physical properties of the element. For chlorine, the electron configuration in its ground state is [Ne] 3s2 3p5, where [Ne] represents the Noble gas core, and the 3s and 3p orbitals are part of the third energy level, accounting for a total of seven valence electrons.

When chlorine forms compounds and interacts with other elements, its electron configuration can change as it achieves different oxidation states. For instance, in the maximum positive oxidation state (+7), chlorine's electron configuration mirrors that of the noble gas argon ([Ne] 3s2 3p6), indicating that all its valence electrons are involved in bonding. In its maximum negative oxidation state (-1), chlorine gains an electron, resulting in an electron configuration of [Ar], resembling that of argon and highlighting the element's desire for a full and stable outer electron shell. Understanding these configurations helps in conceptualizing how chlorine forms bonds and the energy changes involved in these processes.

Group 17 of the periodic table is composed of five elements: fluorine, chlorine, bromine, iodine, and astatine, collectively known as the halogens. These elements are characterized by their seven valence electrons, which makes them one 'electron short' of a full octet. This drives their chemistry and many of their reactions involve gaining an electron to form a -1 oxidation state.

Halogens are highly reactive, with reactivity decreasing down the group as atomic size and mass increase. Fluorine is the most reactive, while astatine is the least, partly due to their positions on the periodic table which affect their electronegativities. Chlorine, situated below fluorine, is less reactive but still forms a range of compounds, both ionic and covalent. Its ability to exist in multiple oxidation states, from -1 up to +7, gives it versatility in chemical reactions and the formation of a wide array of substances from disinfectants to the potent oxidizing agents.