Which of the following elements reacts violently with water?

• A. Sodium (Na)
• B. Gold (Au)
• C. Carbon (C)
• D. Copper (Cu)

Answer: (A)

Verified step by step guidance

1. Step 1: Understand the reactivity of elements with water. Elements that react violently with water are typically highly reactive metals, especially those in Group 1 (alkali metals) and some in Group 2 (alkaline earth metals).
2. Step 2: Identify the properties of each element given: Sodium (Na) is an alkali metal known for its vigorous reaction with water, producing sodium hydroxide and hydrogen gas, often with heat and flames.
3. Step 3: Consider Gold (Au), which is a noble metal and very unreactive; it does not react with water under normal conditions.
4. Step 4: Carbon (C) is a nonmetal and does not react violently with water; it is generally inert in this context.
5. Step 5: Copper (Cu) is a transition metal that is relatively unreactive with water and does not react violently; it may slowly corrode but does not produce violent reactions.