Final answer:
Li will form a cation that is smaller than its neutral atom because losing an electron reduces electron shielding and the size of the electron cloud, whereas Ne does not typically form ions.
Step-by-step explanation:
The atom that will form an ion that is smaller than its neutral atom between Li (lithium) and Ne (neon) is Li. Lithium, when it forms a cation (positively charged ion), loses an electron. This lost electron comes from the outer shell, reducing the electron shielding and allowing the remaining electrons to be pulled closer to the nucleus, ensuing in a smaller lithium ion (Li+) compared to its neutral form. Neon, on the other hand, is a noble gas with a complete valence shell and typically does not form ions.
The process of ion formation and the resulting sizes can be understood through basic physics, where opposite charges attract, leading to smaller cations. The lithium ion is significantly smaller than the neutral lithium atom because removing the 2s1 electron results in a closed shell with a principal quantum number n = 2. In contrast, adding one or more electrons to an atom can cause an increase in size due to electron-electron repulsion, but this is not applicable to neon, which remains neutrally charged and does not form regular ions.