Which atom or ion would you expect to have the smallest radius?

Ne F- Na+ Ne-

What do you think and why?

To determine which atom or ion would have the smallest radius among Ne, F-, Na+, and Ne-, you need to consider their atomic structure and the periodic trends.

Atomic radius generally decreases across a period from left to right on the periodic table and increases down a group.

In this case, let's analyze the given options:
1. Ne (neon) is a noble gas located in Group 18 (also known as Group 8A or Group 0). Noble gases are known to have full valence electron shells. Since Ne is a neutral atom, it has 10 electrons. With a complete valence shell, Ne has a relatively small atomic radius.

2. F- (fluoride ion) has gained an extra electron compared to its neutral counterpart, fluorine (F). When F gains an electron, it has an increased electron-electron repulsion, resulting in a larger ionic radius compared to F.

3. Na+ (sodium ion) has lost an electron compared to its neutral counterpart, sodium (Na). Losing an electron means that the number of protons in the nucleus now exceeds the number of electrons, resulting in a smaller ionic radius compared to Na.

4. Ne- (neon ion) is a hypothetical ion as neon does not generally form ions. However, if it were to gain an electron and become negatively charged, it would have an increased electron-electron repulsion, leading to a larger ionic radius compared to Ne.

Based on this analysis, we can conclude that the ion with the smallest radius would be Na+ (sodium ion) since it has lost an electron, resulting in an increased nuclear charge and a decreased ionic radius compared to the neutral sodium atom.