Part \( \mathbf{A} \) A sodium atom is larger than a silicon atom. True False

**Answer:** **True** **Explanation:** When comparing the atomic sizes of elements, it's essential to consider their positions on the periodic table, specifically their **periods** (rows) and **groups** (columns). - **Sodium (Na):** - **Group:** 1 (Alkali Metals) - **Period:** 3 - **Position:** Far left in the periodic table. - **Silicon (Si):** - **Group:** 14 (Carbon Group) - **Period:** 3 - **Position:** More toward the center-right of the periodic table. **Key Points:** 1. **Atomic Radius Trend Across a Period:** - **Left to Right:** Atomic radius **decreases**. - **Reason:** As you move from left to right across a period, protons are added to the nucleus, increasing the positive charge. This stronger nuclear charge pulls the electrons closer, reducing the atomic size. 2. **Sodium vs. Silicon in Period 3:** - **Sodium** is located on the far left of Period 3. - **Silicon** is located towards the center-right of the same period. - Therefore, **sodium has a larger atomic radius** compared to silicon because it experiences less effective nuclear charge pulling its electrons inward. **Conclusion:** A sodium atom is indeed larger than a silicon atom due to its position in the periodic table and the resulting trends in atomic size across a period.