In the periodic table from left to right in a period, the atomic volume

Options

A. decreases
B. increases
C. remains same
D. first decrease then increases

Explanation

To answer the question regarding the behavior of atomic volume as we move from left to right in a period of the periodic table, we can break down the explanation into clear steps:

### Step-by-Step Solution:

1. **Understanding Atomic Volume**:
- Atomic volume is defined as the volume occupied by one mole of atoms of an element. It is directly related to atomic size (atomic radius).

2. **Trend in Atomic Size**:
- As we move from left to right in a period, the atomic size decreases. This is due to the increase in nuclear charge (the number of protons in the nucleus) without an increase in the number of electron shells.

3. **Effect of Increased Nuclear Charge**:
- The increase in nuclear charge results in a stronger attraction between the nucleus and the electrons. Since the number of electron shells remains constant, the electrons are pulled closer to the nucleus, leading to a decrease in atomic size.

4. **Impact on Atomic Volume**:
- Since atomic volume is directly proportional to atomic size, a decrease in atomic size means that atomic volume will also decrease as we move from left to right across a period.

5. **Exceptions at Noble Gases**:
- However, when we reach the noble gases (the last element in a period), there is a notable increase in atomic volume. This is because noble gases have a complete outer shell, which leads to a more stable configuration and a larger atomic size compared to the halogens (the group before noble gases).

6. **Conclusion**:
- Therefore, the atomic volume first decreases as we move from left to right in a period and then increases when we reach the noble gas element. This trend can be summarized as: **atomic volume decreases until the noble gas, then increases**.

### Final Answer:
The correct answer is that the atomic volume first decreases and then increases as we move from left to right in a period.