1. 2.8 Atoms, Molecules, and the Atmosphere Every person on the planet earth needs air to breathe. But, have you ever wondered what air is made up of? Take a minute and write down what you think makes up air. Now, write down the corresponding percentages for each component of air.

2. Atoms, Molecules, and the Atmosphere Here are the actual components of air: –Oxygen –Nitrogen –Argon (Ar) –Carbon Dioxide (CO 2 )

3. Oxygen Atoms of oxygen can combine to form two different molecules: O 2 is oxygen gas. It makes up 21% of air. and O 3 is ozone. It is formed naturally in the upper layers of the atmosphere. Ozone is important since it absorbs most of the ultraviolet radiation from the Sun. The ozone layer is being destroyed by CFCs or chlorofluorocarbons.

4. Nitrogen Nitrogen makes up 78.02% of the atmosphere. It is not very reactive, which means we can inhale it without causing chemical changes in our lungs. We do not want to inhale nitrogen dioxide since it is a very toxic gas.

5. Argon Argon gas is completely harmless. Almost all of the argon in the atmosphere has leaked out from inside the Earth. Argon is used for filling electric light bulbs and fluorescent tubes. Argon and other gases make up 0.94% of the atmosphere.

6. Carbon Dioxide CO 2 When fossil fuels burn, the two main products are carbon dioxide and water. Carbon dioxide is used by plants. Carbon dioxide makes up 0.03% of the atmosphere.

7. Carbon Monoxide (CO) Produced during combustion when there is a lack of oxygen. For example, if you use a propane barbecue indoors, or if you run an automobile inside a closed garage. The CO molecule is similar to the oxygen molecule in that when carbon monoxide enters the lungs, the body’s red blood cells treats it the same as oxygen and carries it throughout the body. The cells of the body are then starved of the oxygen they need and you could die.

8. Answering Questions about Various Molecules By looking at the chemical formula of a molecule we can answer a variety of questions such as: Which elements are required to construct the molecule? How many atoms, in total, are required to construct the molecule? How many atoms, of each element, are required to construct the molecule? What is the ratio of each type of atom in the molecule? What is the mass of each molecule?

9. An Example C 9 H 8 O 4 or Aspirin Which elements are required to construct the molecule? C = Carbon H = Hydrogen O = Oxygen How many atoms, in total, are required to construct the molecule? 9 + 8 + 4 = 21 total atoms in one molecule of Aspirin How many atoms, of each element, are required to construct the molecule? 9 Carbon, 8 Hydrogen and 4 Oxygen atoms are required to construct one molecule of Aspirin.

10. An Example C 9 H 8 O 4 or Aspirin What is the ratio of each type of atom in the molecule? 9/21 is Carbon 8/21 is Hydrogen 4/21 is Oxygen What is the mass of each molecule? Mass of one molecule of aspirin is calculated as follows: (atomic mass C) x 9 (12) x 9 108 (atomic mass H) x 8 (1) x 8 8 + (atomic mass O) x 4 (16) x 4 64 180 The atomic mass of one molecule of Aspirin is 180.

11. An Example - You do it! Theobromine (Chocolate) - C 7 H 8 N 4 O 2 Which elements are required to construct the molecule? How many atoms, in total, are required to construct the molecule? How many atoms, of each element, are required to construct the molecule? What is the ratio of each type of atom in the molecule? What is the mass of each molecule?

12. An Example - You do it! Theobromine (Chocolate) - C 7 H 8 N 4 O 2 Which elements are required to construct the molecule? C = Carbon H = Hydrogen N = Nitrogen O = Oxygen How many atoms, in total, are required to construct the molecule? 7 + 8 + 4 + 2 = 21 total atoms in one molecule of Chocolate How many atoms, of each element, are required to construct the molecule? 7 Carbon, 8 Hydrogen, 4 Nitrogen and 2 Oxygen atoms are required to construct one molecule of Chocolate.

13. An Example Theobromine (Chocolate) - C 7 H 8 N 4 O 2 What is the ratio of each type of atom in the molecule? 7/21 is Carbon 8/21 is Hydrogen 4/21 is Nitrogen and 2/21 is Oxygen What is the mass of each molecule? Mass of one molecule of chocolate is calculated as follows: (atomic mass C) x 7 (12) x 7 84 (atomic mass H) x 8 (1) x 8 8 (atomic mass N) x 4 (14) x 4 56 + (atomic mass O) x 2 (16) x 2 32 180 The atomic mass of one molecule of chocolate is 180.

14. Assignment Do the “Counting Atoms” worksheet that’s in the shared file –For the molecules containing calcium, aluminum and chromium calculate the atomic mass also. Hand in the worksheet and then move on. Questions 1, 2 and 4 on page 61