Final answer:
Among Be²⁺, O, Be, and O²⁻, the species with the largest radius is D) O²⁻ because the additional electrons increase electron-electron repulsion, resulting in a larger ionic radius.
Step-by-step explanation:
To determine which of the provided options will have the largest radius, we need to consider the effects of nuclear charge, electron-electron repulsion, and electronic configuration on atomic and ionic radii. In general, adding electrons (gaining negative charge) increases the radius due to increased electron-electron repulsion, while removing electrons (forming positive ions) decreases the radius because of the increased hold of the nucleus on the electrons.
Here are the options you provided, compared in terms of radii:
- A. Be²⁺: This is a Beryllium ion with two fewer electrons than the neutral atom. The remaining electrons are drawn closer to the nucleus, smaller than the neutral Be atom.
- B. O: Neutral oxygen atom. It has more electrons than Be, which theoretically provides a larger radius.
- C. Be: Neutral beryllium atom. It has a smaller radius than O because it has fewer electron shells.
- D. O²⁻: This is an Oxygen ion with two additional electrons. This additional electron-electron repulsion means that this ion will have the largest radius out of all the provided options.
Hence, among the four options A. Be²⁺, B. O, C. Be, D. O²⁻, the species with the largest radius is: D. O²⁻.