IONIC RADIUS Meaning and
Definition
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Ionic radius refers to the measurement of the size of an ion, which is an atom or a group of atoms that has an electric charge due to the gain or loss of electrons. Specifically, it relates to the measurement of the distance between the nucleus and the outermost electron shell of an ion.
The ionic radius can vary depending on whether the ion has gained or lost electrons. When an atom loses one or more electrons and forms a positively charged ion or cation, the ionic radius decreases. This is because the electron cloud surrounding the ion becomes smaller and more compact, resulting in a decreased distance between the nucleus and the outermost electrons.
Conversely, when an atom gains one or more electrons and forms a negatively charged ion or anion, the ionic radius increases. The acquired electrons increase the electron cloud's size, causing the distance between the nucleus and the outermost electrons to expand.
Ionic radius is a fundamental concept in chemical bonding as it influences various properties of ionic compounds, such as their crystal structures, lattice energies, and chemical reactivity. It plays a significant role in determining the arrangement of ions in crystals and their ability to pack together. Additionally, the ionic radius affects the strength of the electrostatic attractions between ions, which directly impacts the physical and chemical properties of ionic substances.
Etymology of IONIC RADIUS
The word "ionic radius" is derived from two sources: "ionic" and "radius".
- "Ionic" refers to ions, which are electrically charged particles. Ions are formed when an atom gains or loses electrons to achieve a stable electron configuration. This term originates from the Greek word "ion", meaning "to go". The concept of ions was first introduced in the early 19th century by Michael Faraday.
- "Radius" is a mathematical term referring to the distance from the center of a circle or sphere to its outer edge. The word comes from the Latin word "radius", which means "ray" or "spoke of a wheel".
Therefore, the term "ionic radius" combines these two components to describe the distance from the nucleus to the outermost shell of an ion. It is a measure of the size of an ion, specifically the size of its electron cloud.
