1. Bell Work: Draw the Lewis dot diagram for the following elements: 1.Potassium 2.Phosphorous 3.Calcium 4.Carbon 5.Chlorine

2. Let’s Review Yesterday’s Lesson! Answer the following questions to the best of your ability. Use your notes if you get stuck. Check your answers as we go!

3. 1 1 Section Check Question 1 Electrons are now known to swarm around the nucleus of an atom in a structure known as the _______. A. electron circle B. electron cloud C. electron configuration D. electron swarm

4. 1 1 Section Check Answer The answer is B. The “cloud” includes all the regions where an electron might be found.

5. 1 1 Section Check Question 2 What information can you learn from this diagram?

6. 1 1 Section Check Answer This image is an example of an Lewis dot diagram. It tells you that nitrogen contains five electrons in its outer energy level.

7. 1 1 Section Check Question 3 The _______ an energy level is from the nucleus, the _______ electrons it can hold. A. closer, more B. closer, less C. farther, less D. farther, more

8. 1 1 Section Check Answer The answer is D. The farthest shells contain the greatest number of electrons.

9. Chemical Formulas: Atoms combine (or bond) in predictable numbers. We will use our periodic table to figure out what these numbers are.

10. Each compound has a specific ratio. The ratio compares how many atoms of each element are in the compound. Example: Ammonia’s element ratio is 3 hydrogen atoms to one nitrogen atom. –3 H : 1 N Example: Water’s element ratio is two hydrogens to one oxygen. –2 H : 1 O Example: Salt’s element ratio is one sodium to one chlorine. –1 Na : 1 Cl

11. Knowing the ratio helps us write the chemical formula: A chemical formula uses the chemical symbols to represent the atoms of the elements and their ratios in a chemical compound. The ratio numbers become a subscript behind its element. –A subscript is a number written to the right of a chemical symbol and slightly below. –The subscripts tell you how many atoms of each element are present in the compound. Example: Carbon dioxide is the gas that we exhale. It’s ratio is 1 carbon atom to 2 oxygen atoms or 1 C : 2 O. –The chemical formula for Carbon dioxide is CO 2.

12. Examples of writing the chemical formula: Compound Name Element Present Atom Ratio Chemical Formula Hydrogen chloride Hydrogen and Chlorine 1 H : 1 Cl Water Hydrogen and Oxygen 2 H : 1 O Ammonia Nitrogen and Hydrogen 1 N : 3 H Methane Carbon and Hydrogen 1 C : 4 H Propane Carbon and Hydrogen 3 C : 8 H

13. How do you find the atom ratio of elements in a compound??? We use the ionization # from the periodic table! 4- 3- 2- 1- 0 1+ 2+ These are the ionization #’s for each group.

14. How does this give us the chemical formula? The ionization # of one element in a compound crosses over to the other element in the compound. Example: Ammonia N 3- H 1+ N 1 H 3 The ionization # for H is 1+. The ionization # for nitrogen is 3-. When you write the formula, you cross them over. The element ratio is 3 H : 1 N. The chemical formula is NH 3.

15. Find the element ratio and write the chemical formula for the following: Water (Hydrogen & Oxygen) Salt (Sodium Chloride) Calcium chloride Magnesium oxide