Which of the following primarily determines an element's chemical reactivity?

• A. The atomic mass
• B. The melting point
• C. The number of neutrons
• D. The number of valence electrons

Answer: (D)

Verified step by step guidance

1. Understand that an element's chemical reactivity is mainly influenced by how it interacts with other atoms, which depends on the electrons involved in bonding.
2. Recall that electrons are arranged in shells around the nucleus, and the outermost shell electrons are called valence electrons.
3. Recognize that valence electrons determine how easily an atom can gain, lose, or share electrons to form chemical bonds.
4. Note that atomic mass, melting point, and number of neutrons do not directly affect the chemical bonding behavior of an element.
5. Conclude that the number of valence electrons primarily determines an element's chemical reactivity.