Question

How does the ionic radius of a nonmetal compare with its atomic radius? Explain the change in radius.

Short answer

The ionic radius of a nonmetal is generally larger than its atomic radius when it forms an anion. This is due to the gain of electrons and the resulting increase in electron-electron repulsion, which leads to an expansion of the electron cloud and a larger ionic radius.

Step-by-step solution

Atomic and Ionic Radii Definition

The atomic radius is the measure of the size of an atom. It is typically represented as the distance between the nucleus and the outermost electron shell of an atom. The ionic radius is the measure of the size of an ion formed when an atom gains or loses electrons.

Nonmetals and Ion Formation

Nonmetals are found on the right side of the periodic table. They tend to gain electrons to achieve a stable electron configuration and form negative ions (anions). As a nonmetal gains an electron, its electron configuration resembles that of the nearest noble gas.

Comparison of Ionic and Atomic Radii in Nonmetals

When a nonmetal gains an electron, it forms a negative ion or anion. The addition of an electron increases the electron-electron repulsions in the outer electron shell. The increased repulsion forces the outer electrons to move farther from the nucleus, thus increasing the size of the ion.

Explanation of Change in Radius

The increase in the ionic radius of a nonmetal compared to its atomic radius is due to the gain of electrons and the resulting increase in electron-electron repulsion. This increase in repulsion leads to an expansion of the electron cloud, causing the ion to be larger than the original atom. In summary, the ionic radius of a nonmetal (when it forms an anion) is generally larger than its atomic radius because of the increased electron-electron repulsion within the ion. This repulsion causes the electron cloud to expand, resulting in a larger ionic radius.

Key concepts

Atomic and Ionic Radii Definition

Understanding the size of atoms and ions is crucial when diving into the realm of chemistry. The atomic radius represents the size of an atom. Picture it as an invisible sphere with the atom's nucleus at the center; the radius stretches out to the outer boundary of the atom's electron cloud. The distance usually measures from the nucleus to the outermost electrons that swarm around it.

On the other hand, the ionic radius comes into play when an atom doesn't remain neutral but becomes an ion by either losing or gaining electrons. For ions, the radius is measured in a similar fashion, but since they have different numbers of electrons compared to their parent atoms, their sizes differ. Ions can be larger or smaller than the atoms they originate from—this essentially depends on whether electrons are gained or lost during the ionization process.

Nonmetal Ion Formation

Diving into the nonmetal portion of the periodic table, we see elements that are experts at snagging electrons from their neighbors. Nonmetals prefer to gain electrons—envision them as guests at a party who always reach for extra balloons (electrons). The reason? They want to mimic the stable electronic configurations of noble gases, the VIP guests with the perfect amount of balloons.

When a nonmetal atom grabs an extra electron (or two), it transforms into a negatively charged ion, known as an anion. These anions now have extra electrons hanging around, which alters their properties drastically. With these additional electrons, they now look a lot like their next-door noble gas in terms of electron arrangement, achieving the desired stability that comes with a complete outer shell.

Electron-Electron Repulsion

Imagine a crowded bus where everyone is trying to steer clear of each other—this is similar to electron-electron repulsion. Electrons all carry negative charges, and just like magnets with similar poles, they resist being close together. Within an atom, this push and pull happens within the electron cloud, especially when there's a sudden influx of new electrons—like when a nonmetal forms an anion.

As nonmetals take on extra electrons, the newcomers increase the negative charge within the electron cloud. This leads to electrons jostling for space, pushing against each other to maintain their personal 'bubbles'. The result? An expanded electron cloud. Nonmetals, therefore, end up with a greater ionic radius than their atomic forms due to this very electron repulsion. The added electrons make the electron cloud puff out, giving anions a size upgrade compared to their atom forms.