The minimum energy to ionize an atom is the energy required to

Options

A. add one electron to the atom
B. excite the atom from its ground state to its first excite state
C. remove one outermost electron from the atom
D. remove one innermost electron from the atom

Explanation

To solve the question, "The minimum energy to ionize an atom is the energy required to:", we will analyze the options provided and determine what ionization means in the context of atomic physics.

### Step-by-Step Solution:

1. **Understand Ionization**:
- Ionization refers to the process of removing an electron from an atom, resulting in the formation of an ion. The energy required to remove an electron from an atom is known as ionization energy.

2. **Identify the Options**:
- The question implies there are multiple choices. We need to evaluate each option to determine which one correctly describes the process of ionization.

3. **Evaluate Each Option**:
- **Option A: Add one electron to the atom**: This process is known as electron attachment, not ionization. Therefore, this option is incorrect.
- **Option B: Excite the atom from its ground state to its first excited state**: Excitation involves moving an electron to a higher energy level without removing it from the atom. This is not ionization. Thus, this option is also incorrect.
- **Option C: Remove one outermost electron from the atom**: This is the correct definition of ionization. The outermost electron is typically the valence electron, and its removal requires energy, which is the ionization energy.
- **Option D: Remove one innermost electron from the atom**: While this does involve removing an electron, it is not the typical process referred to when discussing ionization energy, which usually concerns the outermost electron.

4. **Conclusion**:
- Based on the evaluations, the correct answer is **Option C: Remove one outermost electron from the atom**. This accurately describes the minimum energy required to ionize an atom.

### Final Answer:
The minimum energy to ionize an atom is the energy required to remove one outermost electron from the atom.

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