What distinguishes one element from another in terms of atomic structure?

• A. The atomic mass of the element
• B. The number of protons in the nucleus
• C. The number of neutrons in the nucleus
• D. The number of electrons in the outer shell

Answer: (B)

Verified step by step guidance

1. Understand that elements are defined by their atomic number, which is the number of protons in the nucleus of an atom. This is the primary factor that distinguishes one element from another.
2. Recall that the atomic mass of an element is the sum of the number of protons and neutrons in the nucleus, but it does not uniquely identify an element since different elements can have similar atomic masses.
3. Recognize that the number of neutrons in the nucleus can vary even within atoms of the same element, leading to different isotopes, but it does not change the identity of the element.
4. Consider that the number of electrons in the outer shell can affect the chemical properties and reactivity of an element, but it does not define the element itself.
5. Conclude that the defining characteristic of an element is the number of protons in its nucleus, which is unique to each element and determines its position on the periodic table.