* Ionic Bonding: In NaCl, sodium loses an electron to become a positively charged sodium ion (Na⁺), while chlorine gains an electron to become a negatively charged chloride ion (Cl⁻). This transfer of electrons forms an ionic bond.
* Effective Nuclear Charge: When sodium loses its outermost electron, it now has fewer electrons and the same number of protons (positive charges in the nucleus). This means the remaining electrons are pulled in more strongly by the nucleus, resulting in a smaller ionic radius.
* Electron Shielding: Chlorine, on the other hand, gains an electron. This increased number of electrons increases electron-electron repulsion, making the electron cloud larger. Additionally, the extra electron goes into a higher energy level, further increasing the size.
In summary: The loss of an electron in sodium leads to a *stronger* attraction between the remaining electrons and the nucleus, resulting in a smaller ionic radius. The gain of an electron in chlorine leads to a *weaker* attraction between the electrons and the nucleus, resulting in a larger ionic radius.
