Which element in period 3 of the periodic table is known to be a highly reactive metal?

• A. Aluminum (Al)
• B. Silicon (Si)
• C. Phosphorus (P)
• D. Sodium (Na)

Answer: (D)

Verified step by step guidance

1. Identify the elements in period 3 of the periodic table. Period 3 includes the elements: Sodium (Na), Magnesium (Mg), Aluminum (Al), Silicon (Si), Phosphorus (P), Sulfur (S), Chlorine (Cl), and Argon (Ar).
2. Understand the classification of these elements as metals, metalloids, or nonmetals. Metals are typically found on the left side of the periodic table, nonmetals on the right, and metalloids in between.
3. Recall that highly reactive metals in period 3 are usually alkali metals or alkaline earth metals. Sodium (Na) is an alkali metal, known for its high reactivity due to having one valence electron that it readily loses.
4. Compare the reactivity of Aluminum (Al), Silicon (Si), and Phosphorus (P) with Sodium (Na). Aluminum is a metal but less reactive than sodium; Silicon is a metalloid; Phosphorus is a nonmetal, both less reactive metals compared to sodium.
5. Conclude that Sodium (Na) is the highly reactive metal in period 3 because it is an alkali metal with a single valence electron that it easily loses to form positive ions, making it very reactive.