In the modern periodic table, the period indicates the value of

Options

A. Atomic number
B. Atomic mass
C. Principal quantum number
D. Azimuthal quantum number

Answer

To answer the question, "In the modern periodic table, the period indicates the value of," we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Periods in the Periodic Table**:
- The modern periodic table is organized into rows called periods. Each period corresponds to the filling of electron shells.

2. **Identifying the Relationship Between Periods and Electron Configuration**:
- As we move down the periodic table, the elements in each period have electrons that occupy the same principal energy level (or shell). For example:
- The first period contains hydrogen (1s¹).
- The second period contains lithium (2s¹), sodium (3s¹), and so forth.

3. **Recognizing the Principal Quantum Number**:
- The principal quantum number (n) indicates the energy level of the electrons in an atom. It is directly related to the period number in the periodic table.
- For instance, elements in the first period have n=1, those in the second period have n=2, and so on.

4. **Conclusion**:
- Therefore, the period number in the periodic table indicates the value of the principal quantum number (n) of the outermost electrons in the elements of that period.

### Final Answer:
In the modern periodic table, the period indicates the value of the principal quantum number (n).

---