How many elements are accommodated in the fifth period of the long form of the periodic table ?

Options

A. 8
B. 10
C. 18
D. 32

Explanation

To determine how many elements are accommodated in the fifth period of the long form of the periodic table, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Period**: The fifth period of the periodic table is the row that starts with rubidium (Rb) and ends with xenon (Xe).

2. **Count the Orbitals**: In the fifth period, we have the following orbitals that can be filled with electrons:
- 5s (1 orbital)
- 4d (5 orbitals)
- 5p (3 orbitals)

3. **Calculate the Total Number of Elements**:
- The 5s orbital can hold 2 electrons (1 element).
- The 4d orbitals can hold 10 electrons (5 elements).
- The 5p orbitals can hold 6 electrons (3 elements).
- Therefore, the total number of elements in the fifth period is:
\[ 2 \, (\text{from } 5s) + 10 \, (\text{from } 4d) + 6 \, (\text{from } 5p) = 18 \, \text{elements} \]

4. **Conclusion**: The fifth period of the long form of the periodic table accommodates a total of 18 elements.

### Final Answer:
The fifth period of the long form of the periodic table accommodates **18 elements**.

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