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

• A. The total number of neutrons in the nucleus
• B. The number of electrons in the outermost shell
• C. The number of protons and neutrons combined
• D. The atomic mass of the element

Answer: (B)

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 its electrons, especially those in the outermost shell (valence electrons).
2. Recall that neutrons, which reside in the nucleus along with protons, primarily affect the atomic mass and isotope identity but do not directly influence chemical behavior.
3. Recognize that the total number of protons (atomic number) defines the element itself, but chemical properties are more specifically determined by the arrangement of electrons around the nucleus.
4. Focus on the valence electrons because they are involved in forming chemical bonds and reactions, thus determining the element's chemical properties.
5. Conclude that among the options, the number of electrons in the outermost shell is the primary factor that determines the chemical properties of an element.