3.1 Notes Matter and Atomic Structure Name: Matter: Element: 92 elements occur naturally on Earth and in the stars. They are identified with 1,2, and 3 letter abbreviations known as a chemical symbol. Atom : Atoms are made of protons, neutrons, and electrons. Nucleus : proton: electron: Atomic Number: Mass Number: Energy Levels: How many electrons can each energy level hold? 1st Energy Level 3rd energy level 2nd Energy Level 4th energy level HOMEWORK Answer the following questions in cursive and return to me tomorrow!!!! 1. Name the 3 particles that make up an atom and discuss their relative masses. 2. The elements magnesium and calcium have similar chemical properties. Explain why. 3. What are the two most abundant elements in Earth's crust? 1 2 4. Where are valence electrons found? 5. How many naturally occurring elements are there?