1. Elements and Compounds

2. What is an element? A pure substance composed of the same type of atom throughout. Cannot be broken down into simpler substances and still maintain chemical identity On the periodic table

3. Common Elements O₂ (Oxygen gas) N₂ (Nitrogen gas) H₂ (Hydrogen) He (Helium)

4. Element: - Written with one capital letter, may have a lower case letter Chemical Symbol Name of the element

5. Compound: Matter that is composed of two or more different elements chemically combined. Element + Element = Compound – Written in a chemical formula How many molecules, elements? What other compounds do we know?

6. Compounds Compounds are chemically bonded When they bond- change chemical and physical properties (not a mixture) Na- violently reacts with water + Cl- is a poisonous yellow gas ____________________________ NaCl- salt

7. Elements vs. Compounds Compounds can be broken into smaller parts. Elements cannot be broken down into smaller parts. Let's Practice: 1.) H20 2.) NaCl 3.) O₂ 4.) HCl 5.) NaOH

8. Common Compounds H₂O (water) NaCl (Salt) CO₂ (Carbon dioxide HCl (Hydrochloric Acid) NaOH ( Sodium Hydroxide) C₆H₁₂O₆ (glucose= sugar)