Saved Bookmarks
| 1. |
What doesatomicradiusor ionicradiusmean toyou ? |
|
Answer» Solution :Atomicradiusliterallymeanssize ofthe atom. It can be measured either by X- ray orby spectroscopic METHODS. In caseof NON- metals atomicradiusis calledcovalent radius. It isdefinedas one - half thedistancebetweenthe nuclei of TWO covalently bondedatomsof thesameelementin a molecule. Forexamplethe internucleardistancebetweentwochlorineatoms inchlorinemolecule is 198pm. Therefore, the covalent radiusof chlorineatom is198`//`=99pm (0.99 A) . In caseof metals atomicradiusis calledmetallicradius . It isdefinedas one - half thedistancebetweenthe twoadjacentatoms in the crystal lattice .Forexamplethe distancebetweentwoajdacent copper atom in solidcopperis 256 pm,thereforethe metallicradiusof copper is 256`//`2 = 128pm (1.28 A) Ionic radius means size of the ion. An ion can be acation or an anion. The sizeof acationis always smaller than thatof the parentatombecauseloss ofone ormoreelectrons increasesthe effective nuclearcharge. As aresultforce of attractionincreasesand hencethe ionicsizedecreases . On theother hand the size of theanionis always largerthan the parent atom because the additionof one or more electronsdecreasesthe effectivenuclearcharge . As a result the force ofattractiondecreases and hencethe ionic sizeincreases.for examplethe ionic radiusof `Na^(+)` is 95pm whiletheatomicradiusof sodium is 186 pm. One the other handionicradius of fluorideion in136 pmwhereas the atomic radiusof fluorine atom isonly 72pm. |
|