Permeability of cell membrane to `Na^(+)` ion is called ……………… .

Explanation

To answer the question regarding the permeability of the cell membrane to the sodium ion (Na⁺), we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Cell Membrane Permeability**:
- The cell membrane is selectively permeable, meaning it allows certain ions and molecules to pass through while blocking others.

2. **Identifying the Ion in Question**:
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