Two atoms always represent the same element if they have the same number of which subatomic particle?

• A. Neutrons
• B. Protons
• C. Electrons
• D. Total number of protons plus neutrons

Answer: (B)

Verified step by step guidance

1. Understand that atoms are defined by their atomic number, which is the number of protons in the nucleus.
2. Recall that the number of protons determines the identity of an element, meaning all atoms with the same number of protons belong to the same element.
3. Note that neutrons can vary in number within atoms of the same element, leading to different isotopes, but this does not change the element itself.
4. Recognize that electrons affect the charge and chemical behavior but do not define the element's identity.
5. Therefore, the key subatomic particle that must be the same for two atoms to represent the same element is the number of protons.