Between Li And Ne Which Element Has A Larger Atom And Why?
The correct answer and explanation is :
Between Lithium (Li) and Neon (Ne), Lithium (Li) has a larger atomic radius. This is because of the differences in their electron configuration and the effective nuclear charge they experience.
Atomic Radius and Effective Nuclear Charge
The atomic radius is defined as the distance from the nucleus of an atom to the outermost electron shell. It is influenced by two main factors:
- Electron shielding: Electrons in inner shells can “shield” the outer electrons from the full attractive force of the nucleus.
- Effective nuclear charge (Z_eff): This is the net positive charge experienced by an electron, calculated as the total nuclear charge minus the shielding effect of other electrons.
Why Lithium Has a Larger Atomic Radius:
- Electron Configuration:
- Lithium has the electron configuration 1s² 2s¹, meaning it has three electrons in total, with two in the first shell and one in the second.
- Neon has the electron configuration 1s² 2s² 2p⁶, meaning it has ten electrons, with two in the first shell and eight in the second.
- Nuclear Charge:
- Lithium has a nuclear charge of +3 (three protons), whereas Neon has a nuclear charge of +10 (ten protons). Neon’s nucleus exerts a much stronger pull on its electrons compared to Lithium’s nucleus.
- Effective Nuclear Charge:
- In Neon, the electrons experience a stronger effective nuclear charge due to the higher number of protons in the nucleus. This stronger pull draws the electrons closer to the nucleus, leading to a smaller atomic radius.
- In contrast, Lithium has a smaller effective nuclear charge, as it only has three protons. The single 2s electron in Lithium experiences less attraction and is thus farther from the nucleus, resulting in a larger atomic radius.
Conclusion:
Despite both elements being in the same period (Period 2), Lithium has a larger atomic radius than Neon because it has fewer protons in its nucleus, causing it to experience a weaker effective nuclear charge and allowing its outer electron to be more distant from the nucleus. Neon’s higher nuclear charge results in a stronger attraction between the nucleus and electrons, pulling the electrons closer and reducing the atomic radius.