There’s only a small difference in these values and for the most part, the differences aren’t of any concern. The atomic radius that’s often given on charts is frequently a mixture of the values for van der Waals radii, covalent radii, and metallic radii. Sometimes the distance between nonmetallic elements will even be referred to as the covalent radius. The covalent bonding of metals to one another inside of a lattice means that the atomic radius may also be referred to as the metallic radius or covalent radius. The noble gas elements are frequently reported with the van der Waals radius. This is because of the way that the week attraction of the van der Waals forces influences the distances of the two different atoms. The atomic radius of two atoms that are barely touching is sometimes referred to as the van der Waals radius. The electron shells of two different atoms are capable of overlapping with one another, and different circumstances can shift off the distance by which they overlap. They can change because the various configurations of ions and atoms can influence the distance between the nuclei of the ions. Take note that both the ionic radius and atomic radius aren’t fixed values. Photo: Popnose via Wikimedia Commons, CC-BY-SA 3.0 The atomic radii have been listed in picometers. The atomic radii of various elements as cations (red), anions (blue), and neutral atoms. That said, most measurements of ionic radius fall between 30 pm to 200 pm. Ionic radius is often measured with x-ray crystallography or with similar devices and systems, and implementing a different measurement system can change the measured value of the ionic radius. It’s difficult to get the exact measurement of the ionic radius because they can fluctuate depending on the method used to determine the ion’s size. This electron increases the overall size of the electron cloud and can make the ionic radius bigger.

In contrast, anions (negatively charged ions) have an additional electron. This is because a cation has an electron removed from its shell, so the electrons which remain experience a greater attraction to the nucleus and are drawn towards it. Cations, or positively charged ions, are usually smaller than a neutral atom of the element would be. Whether it is larger or smaller depends on the kind of electric charge the ion has.

“A physicist is just an atom’s way of looking at itself.” - Niels Bohr The ionic radius can easily be a little smaller or larger than the atomic radius, which is the radius a neutral atom of the element possesses. An electron shell’s boundary is difficult to get an exact reading on, so the ions of an atom are typically treated as if they were solid spheres. The value of the ionic radius is half the distance between two ions which are just barely touching one another. Defining Ionic RadiusĪs mentioned, the ionic radius of an ion is measured when the atom is in a crystal lattice. Ionic radius tends to increase as you move from top to bottom down the periodic table, and it tends to decrease as you move left to right across the periodic table. The ionic radius trend refers to how the ionic radius of elements follows a predictable trend across the periodic table of the elements. The ionic radius is defined as half the distance between two different atoms that are just barely touching. The ionic radius of an atom is a measurement of the atom’s ion when the atom is within a crystal lattice.

Fluorine atomic radius