The correct answer is option (C)proton. Since the electronic configuration of Hydrogen atom is 1s¹. So, due to ionisation enthalpy, the atom will lose its one electron present at the outermost shell. So hydrogen atom will have only a proton in its nucleus i. e. H+ (since number of neutrons in hydrogen is 0, deuterium -1, tritium-2).
H(g) → H+(g) + e-

The ionisation of hydrogen atom would give rise to:

a. Hydride ion:
- The hydride ion (H-) is formed when a hydrogen atom gains an extra electron.
- This occurs when a hydrogen atom is reduced, meaning it gains an electron to achieve a stable electron configuration.
- The hydride ion has a charge of -1 and is often found in ionic compounds, such as sodium hydride (NaH) or lithium hydride (LiH).

b. Hydronium ion:
- The hydronium ion (H3O+) is formed when a hydrogen atom loses its electron and combines with a water molecule.
- This occurs in aqueous solutions, where water acts as a solvent and can donate a proton (H+) to a solute.
- The hydronium ion is a key species in acid-base chemistry and is often found in acidic solutions.

c. Proton:
- A proton is a subatomic particle with a positive charge (+1) that is found in the nucleus of an atom.
- When a hydrogen atom loses its electron, it becomes a proton.
- Protons are fundamental particles and are involved in various atomic and nuclear processes.

d. Hydroxyl ion:
- The hydroxyl ion (OH-) is formed when a water molecule loses a proton (H+).
- This occurs in basic solutions, where water acts as a base and can accept a proton from a solute.
- The hydroxyl ion is a key species in basic chemistry and is often found in alkaline solutions.

Explanation:
- The ionisation of a hydrogen atom refers to the process of removing an electron from a hydrogen atom, resulting in the formation of a positively charged ion.
- This can occur through various means, such as exposure to high-energy radiation or interaction with other atoms or molecules.
- The resulting ion can have different properties depending on the specific conditions and environment.
- In the case of a hydrogen atom, the ionisation can give rise to a hydride ion, hydronium ion, proton, or hydroxyl ion, depending on the context.
- Each of these ions plays a unique role in different chemical reactions and can have significant implications in various fields of science, including chemistry, physics, and biology.
- Understanding the ionisation of hydrogen atoms is crucial for comprehending fundamental concepts in these disciplines and for advancing scientific knowledge and technological applications.