Why anion is larger than cation

Comparison of ion sizes to atom sizes for Groups 1, 2, 13, 16 and The atoms are shown in gray. Groups 1, 2, and 13 are metals and form cations, shown in red. Groups 16 and 17 are nonmetals and form anions, shown in blue. The removal of electrons always results in a cation that is considerably smaller than the parent atom.

When the valence electron s are removed, the resulting ion has one fewer occupied principal energy level, so the electron cloud that remains is smaller. Another reason is that the remaining electrons are drawn closer to the nucleus because the protons now outnumber the electrons. One other factor is the number of electrons removed. The potassium atom has one electron removed to for the corresponding ion, while calcium loses two electrons. The addition of electrons always results in an anion that is larger than the parent atom.

When the electrons outnumber the protons, the overall attractive force that the protons have for the electrons is decreased. Xe Cs Ba La Hf Ta W Re Os Ir Pt Au Hg Tl Pb Bi Po Rn Fr Ra Ac Rf Db Sg Bh Hs Uuq n. Ce Pr Nd Pm Sm Eu This results in a larger atomic radius. Moving down in a group, the electronegativity decreases due to an increase in the distance between the nucleus and the valence electron shell, thereby decreasing the attraction, making the atom have less of an attraction for electrons or protons.

An atomic mass symbol: m a is the mass of a single atom of a chemical element. It includes the masses of the 3 subatomic particles that make up an atom: protons, neutrons and electrons. Metal atoms lose the electron, or electrons, in their highest energy level and become positively charged ions. Non- metal atoms gain an electron, or electrons, to become negatively charged ions. Ionic bond. Ionic bond, also called electrovalent bond, type of linkage formed from the electrostatic attraction between oppositely charged ions in a chemical compound.

The atom that loses the electrons becomes a positively charged ion cation , while the one that gains them becomes a negatively charged ion anion. The covalent radius , r cov , is a measure of the size of an atom that forms part of one covalent bond. The atomic radius of a chemical element is the distance from the centre of the nucleus to the outermost shell of the electron. Ionic radius also increases with increasing coordination number , the electron cloud is drawn out by the presence of more surrounding ions.

This is because there are fewer electrons in the outer shells of the ions. The sizes of anions are relatively large because there are more electrons in their outermost shells. Why is anion larger than the parent atom? Cations and Anions Neutral atoms that have lost an electron exhibit a positive charge and are called cations. Measurement and Factors Affecting Ionic Radii The ionic radius of an atom is measured by calculating its spatial proportions in an ionic bond with another ion within a crystal lattice.

References Housecroft, Catherine E. Inorganic Chemistry. England: Pearson Education Limited, Shannon R. Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides. Acta Crystallographica ;32 5 : Jensen B. Journal of Chemical Education ;86 6 Oliver, Johnson. Ionic Radii for Spherical Potential Ions.

Inorganic Chemistry ;12 4 Birkholz, Mario. Crystal-field induced dipoles in heteropolar crystals II: Physical significance. Problems Why are cations smaller and anions larger than their respective atoms?