Elements in the same group have similar chemical properties because they share the same number of what in their valence shell?

• A. Electrons
• B. Protons
• C. Neutrons
• D. Quarks

Answer: (A)

The key idea is that chemical properties are governed by the electrons in the outermost shell, the valence electrons. Elements in the same group have the same number of valence electrons, so they tend to bond and react in similar ways. Those outer electrons are the ones you gain, lose, or share during reactions to reach a stable configuration, which is why members of a group behave alike. Protons and neutrons live in the nucleus and influence identity and mass, not how atoms bond, and quarks are subnuclear components not involved in valence chemistry. For example, having one valence electron makes an element prone to losing it to form a +1 ion, while seven valence electrons make another group want to gain one to complete an octet.