1. Aim: What are isotopes and how do they affect the atomic mass of elements? Do Now: Copy vocabulary - Atomic number- number of protons in an atom. Mass number- total number of protons plus neutrons (p + n) Isotopes- atoms of the same element with different numbers of neutrons (and therefore different masses.) Essential Questions : “Protons are positively charged, and like charges repel.” Explain how protons and neutrons form a stable nucleus in spite of this electrostatic repulsion. How are isotopes of the same element alike? Different? Describe the major differences between electrons, protons, and neutrons in terms of size, mass, and location. How do chemists write symbols for isotopes of elements? Why are atomic masses in decimal form on Periodic Table of the Elements if protons and neutrons are whole entities?

2. Aim: What are isotopes and how do they affect the atomic mass of elements? Essential Questions : “Protons are positively charged, and like charges repel.” Explain how protons and neutrons form a stable nucleus in spite of this electrostatic repulsion. How are isotopes of the same element alike? Different? Describe the major differences between electrons, protons, and neutrons in terms of size, mass, and location. How do chemists write symbols for isotopes of elements? Why doesn’t the mass number take the mass of electrons into account? (mass number = p + n) Why are atomic masses in decimal form on Periodic Table of the Elements if protons and neutrons are whole entities?

3. Aim: What are isotopes and how do they affect the atomic mass of elements? Do Now: Copy vocabulary - Atomic number- number of protons in an atom. Mass number- total number of protons plus neutrons (p + n) Isotopes- atoms of the same element with different numbers of neutrons (and therefore different masses.)