According to Lewis concept, an acid is a substance which

Options

A. Accepts protons
B. Donates protons
C. Accepts a lone pair of electrons
D. Donates a lone pair of electrons

Answer

**Step-by-Step Solution:**

1. **Understanding the Lewis Concept**: The Lewis concept of acids and bases is based on the donation and acceptance of electron pairs. According to this concept, an acid is defined as a substance that can accept a pair of electrons.

2. **Definition of Lewis Acid**: A Lewis acid is any species that can accept an electron pair from another species. This means that Lewis acids are electron pair acceptors.

3. **Examples of Lewis Acids**: Common examples of Lewis acids include metal cations (like Fe³⁺, Al³⁺), molecules like BF₃ (Boron trifluoride), and other compounds that can accept electron pairs due to their electron-deficient nature.

4. **Understanding Lewis Bases**: In contrast, a Lewis base is defined as a substance that can donate a pair of electrons. For example, ammonia (NH₃) is a Lewis base because it has a lone pair of electrons that it can donate.

5. **Conclusion**: Therefore, according to the Lewis concept, an acid is a substance that accepts a lone pair of electrons, making it a Lewis acid.

**Final Answer**: According to the Lewis concept, an acid is a substance that accepts a lone pair of electrons.

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