Q: Why is the Van der Waals Radius always greater than the Covalent Radius?ДЄns: The Van der Waals forces of attraction are weak. As a result, the attraction of the nucleus for the electron decreases. The valence electrons lie farther and farther away from the nucleus. A new energy shell is added at each succeeding element. As we move down the group, the principal quantum number increases. The atomic radii of elements increase with an increase in the atomic number from top to bottom in a group. Therefore, the atomic size of inert gas in a period is much higher than that of preceding halogen Van der Waals radius is larger than the covalent radius. We express the atomic size in terms of Van der Waals radius since they do not form covalent bonds. This is because inert gases have completely filled orbitals. The atomic radius abruptly increases as we move from halogens to the inert gas.This results in a decrease in the atomic radius as we move from left to right in a period. This makes each individual shell smaller and smaller. This enhanced nuclear charge pulls the electrons of all the shells closer to the nucleus. As we move from left to right in a period, the nuclear charge increases by 1 unit in each succeeding element while the number of shells remains the same.The size of atoms of inert gases is larger than those of the preceding halogens. After nitrogen, atomic size increases for Oxygen and then decreases for fluorine. The atomic size of nitrogen is the smallest. TheВ halogens at the extreme right of the periodic table have theВ smallest size. TheВ alkali metals at the extreme left of the periodic table have the largest sizeВ in a period. The C ovalent and Van der Waals radii decrease with an increase in the atomic number as we move from left to right in a period.Variation of Atomic Radii in the Periodic Table Variation Within a Period Read about Metallic and Non-Metallic characters here. The metallic radius of Potassium is 231 pm while its covalent radius is 203 pm. For example, the metallic radius of sodium is 186 pm whereas its covalent radius as determined by its vapor which exists as Na 2В is 154 pm. Thus, a metallic radius is always longer than its covalent radius. In a covalent bond, a pair of electrons is strongly attracted by the nuclei of two atoms. In a metallic lattice, the valence electrons are mobile, therefore, they are only weakly attracted by the metal ions or kernels. It is one half the internuclear distance between the two adjacent metal ions in the metallic lattice. Each kernel is simultaneously attracted by a number of mobile electrons and each mobile electron is attracted by a number of metal ions.ДЇorce of attraction between the mobile electrons and the positive kernels is called the metallic bond. Know about Electron Gain Enthalpy? 3) Metallic RadiusДЄ metal lattice or crystal consists of positive kernels or metal ions arranged in a definite pattern in a sea of mobile valence electrons. Therefore, the Van der Waals radius of the chlorine atom is 180 pm. The magnitude of the Van der Waals radius is dependent on the packing of the atoms when the element is in the solid-state.ДЇor example, the internuclear distance between two adjacent chlorine atoms of the two neighboring molecules in the solid-state is 360 pm. It is one half the distance between the nuclei of two identical non-bonded isolated atoms or two adjacent identical atoms belonging to two neighboring molecules of an element in the solid-state. The internuclear distance between two bonded atoms is called theВ bond length. Therefore, r covalentВ = ВЅ (internuclear distance between two bonded atoms). Historical Development of the Periodic TableД¬ovalent radius is one half the distance between the nuclei of two covalently bonded atoms of the same element in a molecule.Browse more Topics Under Classification Of Elements And Periodicity In Properties Therefore, we will study these three types of radius because they are vital for a better understanding of the subject. In other words, it is the distance from the center of the nucleus to the point up to which the density of the electron cloud is maximum.ДЄtomic radii are divided into three types:

Click on 'Element Atomic Number', 'Element Symbol', 'Element Name' and 'Element Atomic Radius (Calculated)' headers to sort.Atomic radius is the distance from the centre of the nucleus to the outermost shell containing electrons. This Atomic Radius (Calculated) table gives the Atomic Radius (Calculated) of all the elements of periodic table in pm.

Al atomic radius