Which of the following elements is the most reactive?

• A. Oxygen (O)
• B. Carbon (C)
• C. Nickel (Ni)
• D. Sodium (Na)

Answer: (D)

Verified step by step guidance

1. Understand that reactivity in elements depends on their position in the periodic table and their tendency to lose or gain electrons to achieve a stable electron configuration.
2. Recall that metals, especially alkali metals like Sodium (Na), tend to be highly reactive because they have a single electron in their outermost shell that they can easily lose.
3. Compare the elements given: Oxygen (O) is a nonmetal that tends to gain electrons, Carbon (C) is a nonmetal with moderate reactivity, Nickel (Ni) is a transition metal with relatively low reactivity, and Sodium (Na) is an alkali metal known for its high reactivity.
4. Recognize that Sodium (Na) is the most reactive among these because it readily loses its one valence electron to form a positive ion, making it highly reactive, especially with water and oxygen.
5. Conclude that the element with the highest reactivity in the list is Sodium (Na), due to its position as an alkali metal and its electron configuration.