Which part of an atom primarily determines its chemical properties?

• A. The number of protons in the nucleus
• B. The total mass of the atom
• C. The number of valence electrons
• D. The number of neutrons

Answer: (C)

Verified step by step guidance

1. Understand that the chemical properties of an atom are mainly influenced by how it interacts with other atoms, which depends on the electrons involved in bonding.
2. Recall that electrons are arranged in energy levels or shells around the nucleus, and the electrons in the outermost shell are called valence electrons.
3. Recognize that valence electrons determine an atom's ability to gain, lose, or share electrons, which directly affects its chemical reactivity and bonding behavior.
4. Note that while the number of protons defines the element and the number of neutrons affects isotopes, these do not primarily control chemical properties.
5. Conclude that the number of valence electrons is the key factor that primarily determines an atom's chemical properties.