Activity A: Subatomic particles Get the Gizmo ready: Use the arrows to create an atom with two protons, two neutrons, and two electrons. Turn on Show element name. Question: What are the properties of protons, neutrons, and electrons? Observe: Turn on Show element symbol and Element notation. Three numbers surround the element symbol: the mass number (A), electrical charge (no number is displayed if the atom is neutral), and the atomic number (Z). Investigate: Watch how the numbers change as you add or remove particles. A. Which number is equal to the number of protons in the atom? B. How can you calculate the number of neutrons (N) in an atom? C. Which particle (proton, neutron, or electron) has a Positive charge? Negative charge? No charge at all? Analyze: An isotope is an alternative form of an element. Each isotope of an element has the same number of protons, but a different number of neutrons. The isotope is represented by the atomic symbol and mass number, such as He-4. Some isotopes are stable, while others are radioactive, which means the atoms decay over time and emit radiation. A. What are the stable isotopes of carbon? B. What are the stable isotopes of nitrogen? C. List two radioactive isotopes of oxygen: