Which of the following primarily determines the chemical properties of an element?

• A. The number of valence electrons
• B. The atomic mass
• C. The total number of protons and neutrons
• D. The number of neutrons

Answer: (A)

Verified step by step guidance

1. Understand that the chemical properties of an element are mainly influenced by how it interacts with other atoms, which depends on the electrons involved in bonding.
2. Recall that valence electrons are the electrons in the outermost shell of an atom and are responsible for forming chemical bonds.
3. Recognize that the atomic mass (sum of protons and neutrons) affects physical properties like mass but does not directly determine chemical behavior.
4. Note that the total number of protons and neutrons defines the identity and isotope of the element but does not primarily control chemical reactivity.
5. Conclude that the number of valence electrons primarily determines the chemical properties of an element because they dictate how the element bonds and reacts with others.