Question

Household Products Why do the elements chlorine, used in laundry bleach, and iodine, a nutrient added to table salt, have similar chemical properties?

Short answer

Chlorine and iodine have similar chemical properties because they both belong to Group 17 (Halogens) in the Periodic Table and have the same number of valence electrons in their outer electron shells. Their electron configurations are $[Ne]3s^{2}3p^5$ for chlorine and $[Kr]5s^{2}4d^{10}5p^5$ for iodine. Both elements are highly electronegative and tend to gain an electron to achieve a stable, full electron configuration, resulting in the formation of anions with a charge of -1. Their similar chemical properties and reactivity allow them to form salts and function as disinfecting agents in household products like laundry bleach and iodized table salt.

Step-by-step solution

Determine the position of chlorine and iodine on the Periodic Table.

Chlorine belongs to the Group 17 (Halogens) and Period 3, while iodine belongs to Group 17 and Period 5. Elements within the same group have similar chemical properties because they have the same number of valence (outer shell) electrons.

Examine the electron configuration of both elements.

The electron configuration of chlorine is $[Ne]3s^{2}3p^5$, and that of iodine is $[Kr]5s^{2}4d^{10}5p^5$. The similarities in their chemical properties arise from the 5 valence electrons in the p orbitals of both elements. Both chlorine and iodine need one more electron to complete their outer electron shell and achieve a stable electron configuration.

Assess the tendency of both elements to gain electrons.

Elements in Group 17 are highly electronegative, meaning they have a strong tendency to attract electrons. Chlorine and iodine are likely to gain an electron to complete their outer electron shell and achieve a stable, full (noble gas) electron configuration. This tendency results in the formation of negative ions (anions) with a charge of -1 like $C{l}^{-}$ and $I^{-}$.

Compare the chemical reactivity of chlorine and iodine.

Since both elements have a similar electron structure, they have similar chemical properties and reactivity. They can react with metals to form salts, like sodium chloride (NaCl) or potassium iodide (KI). Both chlorine and iodine are also widely used as disinfecting agents, due to their reactivity and ability to kill bacteria and other pathogens by disrupting their cell structures.

Understand the connection between their electron configuration and their application in household products.

Laundry bleach that contains chlorine (as sodium hypochlorite) uses its strong oxidizing properties to break down stains and remove unwanted colors. Iodine, which is added to table salt as potassium iodide, is an essential nutrient for humans and functions as a component of the thyroid hormones, which regulate metabolism, growth, and development. The chemical similarities of chlorine and iodine arise from their electron structure and are the basis of their applications in these household products.

Key concepts

Periodic Table Group Trends

Understanding the periodic table is crucial for grasping why elements exhibit certain behaviors and properties. In the example of chlorine and iodine, we see the influence of group trends. Elements grouped together in the periodic table, such as the halogens in Group 17, have distinct similarities because they share the same number of valence electrons.

As you move down a group, the elements have more energy levels, meaning they get larger, and the valence electrons are farther from the nucleus. This affects the atomic radius, ionization energy, and electronegativity. Despite these changes, the underlying chemical behavior remains consistent within a group, enabling elements like chlorine and iodine to form similar types of compounds and participate in similar reactions.

Electron Configuration

The electron configuration of an atom reveals the distribution of electrons among the different energy levels and subshells. For halogens like chlorine and iodine, the electron configuration ends with the p subshell nearly filled. This is significant because the arrangement of electrons determines how atoms interact with each other.

Chlorine, with its electron configuration of $[Ne]3s^{2}3p^5$, and iodine, having $[Kr]5s^{2}4d^{10}5p^5$, both lack one electron from having a completely filled outermost p subshell. This one missing electron plays a central role in the halogens' high reactivity and is the driving force behind their ability to form bonds, particularly ionic bonds, with other elements.

Chemical Reactivity

The chemical reactivity of an element is often predicted by its position on the periodic table. Halogens, located in Group 17, are highly reactive nonmetals. Their reactivity is primarily due to their electronegativity, being high compared to other elements. They are always one electron short of a complete outer shell, which pushes them to gain an electron in chemical reactions.

For chlorine and iodine, this means they readily form negative ions ($C{l}^{-}$ and $I^{-}$) by accepting an electron from other atoms, leading to stable, electron-filled configurations. This property is why they're both potent in antibacterial applications and why they form salts when reacting with metals. The reactivity also ensures that these elements are significant in various industrial and medical applications.

Valence Electrons

The concept of valence electrons is neatly demonstrated by the behavior of chlorine and iodine. These are the electrons in the outermost shell of an atom and they play a pivotal role in chemical bonding and reactivity. Both chlorine and iodine have seven valence electrons, just one short of the stable configuration of eight, known as an octet.

This 'one electron short' status makes them highly motivated to engage in chemical reactions to either share or take an electron from another atom, thus achieving a full valence shell. It is this quest for an octet that underlies many of the characteristic reactions of halogens, including the ones they are used for in household products like bleach and iodized table salt.