Which of the following best describes a hydrogen ion?

• A. A hydrogen atom that has gained an extra electron, forming H−
• B. A hydrogen atom with no protons and one electron
• C. A hydrogen atom with two protons and one electron
• D. A hydrogen atom that has lost its only electron, forming H+

Answer: (D)

Verified step by step guidance

1. Recall that a hydrogen atom consists of one proton and one electron in its neutral state.
2. Understand that a hydrogen ion (H+) is formed when the hydrogen atom loses its only electron.
3. Recognize that losing the electron leaves the hydrogen ion with just one proton and no electrons, giving it a positive charge.
4. Compare the options: an atom that gains an electron becomes H⁻ (hydride ion), which is different from H⁺.
5. Conclude that the best description of a hydrogen ion is a hydrogen atom that has lost its only electron, forming H⁺.