The number of elements in 5th and 6th period of periodic table are respectively

Options

A. 8, 18
B. 18, 18
C. 18, 32
D. 18, 28

Answer

To determine the number of elements in the 5th and 6th periods of the periodic table, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Structure of the Periodic Table**: The periodic table is organized into periods (rows) and groups (columns). Each period corresponds to the filling of electron shells.

2. **Identify the Number of Elements in Each Period**:
- The number of elements in a period corresponds to the maximum number of electrons that can occupy the orbitals in that period.

3. **Count the Elements in the 5th Period**:
- The 5th period includes the filling of the 5s, 4d, and 5p orbitals.
- The distribution of electrons is as follows:
- 5s can hold 2 electrons.
- 4d can hold 10 electrons.
- 5p can hold 6 electrons.
- Therefore, the total number of elements in the 5th period is:
\[ 2 \, (from \, 5s) + 10 \, (from \, 4d) + 6 \, (from \, 5p) = 18 \, elements \]

4. **Count the Elements in the 6th Period**:
- The 6th period includes the filling of the 6s, 4f, 5d, and 6p orbitals.
- The distribution of electrons is as follows:
- 6s can hold 2 electrons.
- 4f can hold 14 electrons.
- 5d can hold 10 electrons.
- 6p can hold 6 electrons.
- Therefore, the total number of elements in the 6th period is:
\[ 2 \, (from \, 6s) + 14 \, (from \, 4f) + 10 \, (from \, 5d) + 6 \, (from \, 6p) = 32 \, elements \]

5. **Conclusion**:
- The number of elements in the 5th period is **18**.
- The number of elements in the 6th period is **32**.

### Final Answer:
The number of elements in the 5th and 6th periods of the periodic table are respectively **18** and **32**.

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