Which of the following is the fundamental building block of all matter?

• A. Atoms
• B. Molecules
• C. Protons
• D. Ions

Answer: (A)

Verified step by step guidance

1. Understand the question is asking for the fundamental building block of all matter, which means the smallest unit that retains the properties of an element and makes up everything around us.
2. Recall that atoms are the basic units of chemical elements and consist of protons, neutrons, and electrons. They combine to form molecules.
3. Recognize that molecules are made up of two or more atoms bonded together, so they are not the most fundamental unit but rather a combination of atoms.
4. Note that protons are subatomic particles found inside atoms, so while important, they are components of atoms, not the fundamental building blocks themselves.
5. Understand that ions are atoms or molecules that have gained or lost electrons and carry a charge, so they are derived forms of atoms, not more fundamental.