Hydrogen has :

Options

A. (a) half filled subshell
B. (b) half filled shell
C. (c) one electron in valence shell
D. (d) half filled orbital

Answer

To answer the question about hydrogen, we will analyze its electronic configuration and the implications of that configuration step by step.

### Step-by-Step Solution:

1. **Identify the Atomic Number of Hydrogen**:
- Hydrogen has an atomic number of 1, which means it has 1 proton and, in a neutral atom, 1 electron.

**Hint**: Remember that the atomic number indicates the number of protons and electrons in a neutral atom.

2. **Determine the Electronic Configuration**:
- The electronic configuration of hydrogen can be represented as \(1s^1\). This means there is one electron in the 1s subshell.

**Hint**: The notation \(1s^1\) indicates that there is one electron in the first energy level (n=1) and in the s subshell.

3. **Analyze the Half-Filled Subshell**:
- The s subshell can hold a maximum of 2 electrons. Since hydrogen has only 1 electron in the 1s subshell, it is considered half-filled.

**Hint**: A subshell is considered half-filled when it contains exactly half of the maximum number of electrons it can hold.

4. **Check the Half-Filled Shell**:
- The first shell (n=1) consists only of the s subshell. With 1 electron in the 1s subshell, the shell is also considered half-filled.

**Hint**: A shell is half-filled if the number of electrons is equal to half of the maximum capacity of that shell.

5. **Identify the Valence Electron**:
- The valence shell for hydrogen is the first shell (n=1), which contains the 1s subshell. Since there is 1 electron in this shell, it is the valence electron.

**Hint**: The valence shell is the outermost shell of an atom, and the electrons in this shell are called valence electrons.

6. **Confirm Half-Filled Orbital**:
- The 1s subshell is considered an orbital, and since it contains 1 electron, it is also half-filled.

**Hint**: An orbital is half-filled when it contains one electron, as it can hold a maximum of two.

### Conclusion:
All statements regarding hydrogen's electronic configuration are correct:
- It has a half-filled subshell.
- It has a half-filled shell.
- It has one electron in the valence shell.
- It has a half-filled orbital.