Reasons for Iodine having a smaller size than Lithium atom:
- Number of Protons and Electrons:
- Iodine (I) has 53 protons and electrons, while Lithium (Li) has 3 protons and electrons. The greater number of protons in Iodine leads to a stronger nuclear pull on the electrons, resulting in a smaller atomic size.
- Number of Electron Shells:
- Iodine has more electron shells (7) compared to Lithium (2). The additional electron shells in Iodine increase the atomic size due to increased electron-electron repulsion, making it larger than Lithium.
- Effective Nuclear Charge:
- The effective nuclear charge experienced by the outermost electrons in Iodine is lower compared to Lithium. This is due to the shielding effect of inner electrons in Iodine, which results in a larger atomic size.
- Atomic Radius Trend:
- Moving down a group in the periodic table, atomic size generally increases due to the addition of new electron shells. However, moving across a period from left to right, atomic size decreases due to increased nuclear charge pulling electrons closer.
In conclusion, the combination of a higher number of protons, greater electron-electron repulsion from additional electron shells, and the shielding effect of inner electrons results in Iodine having a smaller size than Lithium atom.