Arrange the following species in order of decreasing radius: S, Cl^-, Ar, K^+ . Explain your ans

step 1 So in chemistry we have the periodicity that just refers to the trends that repeat throughout th

Arrange the following species in order of decreasing radius:...

Key Concepts

Atomic and Ionic Radii

Atomic radius is a measure of the size of an atom, while ionic radius refers to the size of an ion. The method of measurement differs—atomic radii might be defined in terms of covalent or van der Waals interactions, whereas ionic radii are often derived from distances between nuclei in ionic crystals. Understanding these definitions is essential when comparing the sizes of neutral atoms and ions, which can have quite different radii even if they have similar numbers of electrons.

Periodic Trends in Atomic Size

In the periodic table, atomic size generally decreases from left to right across a period due to increasing effective nuclear charge, and increases from top to bottom as additional electron shells are added. This trend helps in predicting the relative sizes of atoms, so when comparing species from the same period, one expects that a higher nuclear charge (with a similar or identical electron configuration) will pull the electrons closer, yielding a smaller radius.

Isoelectronic Series and Effective Nuclear Charge

An isoelectronic series comprises species that have the same number of electrons but different numbers of protons. Within such a series, the effective nuclear charge—the net positive charge experienced by the electrons—increases with the number of protons. Therefore, species with a higher nuclear charge have their electrons drawn in more tightly, resulting in a smaller radius. This reasoning is crucial when comparing ions like Cl–, Ar, and K+, which all have 18 electrons but differ in nuclear charge.

Electron–Electron Repulsions

Electron–electron repulsions affect the size of an electron cloud; additional electrons in a species cause increased repulsion, which can expand the radius. In ions, the balance between nuclear attraction and these repulsive forces determines the final size, making it particularly important when comparing anions, neutrals, and cations even if they are isoelectronic or belong to neighboring elements in the periodic table.

Transcript

Please give Ace some feedback