1. WWHS CHEMISTRY @WOODROWCHEM Do Now: 1

2. WWHS CHEMISTRY @WOODROWCHEM Dissecting the Do Now: 2 Check your answers up front when you are done! Make sureyou understand the problems!

3. WWHS CHEMISTRY @WOODROWCHEM “Let there be bread, water, and salt for all.” – Nelson Mandela 3

4. WWHS CHEMISTRY @WOODROWCHEM 4 What makes salt so important?

5. WWHS CHEMISTRY @WOODROWCHEM What you should already know… Salt is an ionic compound – It is made of metal Na + ions and non-metal Cl - ions that are attracted to each other. Key Questions this Week: – Why does salt form in the first place? (Monday) – What kind of properties does salt have and why? (Tuesday) – Why can salt dissolve in water and participate in biological processes? (Wednesday) 5

6. WWHS CHEMISTRY @WOODROWCHEM Today’s Learning Target: Find out why salt forms by… Explaining the ionization energy of an electrons using Coulomb’s Law. 6

7. WWHS CHEMISTRY @WOODROWCHEM Linking to Physics 7 Isaac Newton relates gravitational force to mass and distance Derives the equation:

8. WWHS CHEMISTRY @WOODROWCHEM What does this mean? 8 Bigger objects (like bigger planets) have more force of gravity. Because radius (distance) is in the denominator, the farther apart two objects are the weaker their force of gravity.

9. WWHS CHEMISTRY @WOODROWCHEM Two asteroids with identical mass are approaching earth. Asteroid 1 is 630,000 km away, while asteroid 2 is 635,000 km away. Which exerts more force on the earth? A.Asteroid 1 B.Asteroid 2 9

10. WWHS CHEMISTRY @WOODROWCHEM Can we apply that thinking to atoms ? There are three total electrons in a lithium atom, which has a configuration of 1s 1 2s 1. Which electron experiences the weakest force of attraction to the nucleus? A.1s 1 electron B.1s 2 electron C.2s 2 electron 10

11. WWHS CHEMISTRY @WOODROWCHEM Coulomb’s Law tells us about electrostatic force, instead of gravitational force. Instead of mass, we use charge. 11 Distance between charges matters

12. WWHS CHEMISTRY @WOODROWCHEM Coulomb’s Law tells us about an electron’s ionization energy Ionization energy = the energy input needed to steal an atom’s electron. 12 Higher ionization energy = harder to remove an electron Lower ionization energy = easier to remove an electron

13. WWHS CHEMISTRY @WOODROWCHEM 13

14. WWHS CHEMISTRY @WOODROWCHEM Left to Right Across the Periodic Table What increases, generally, as we move from left to right across the periodic table? – Protons (Atomic Number) Think about Coulomb’s Law. If the positive charge from protons increases, what happens to the force of attraction? – Increases Should it be harder (high ionization energy) or easier (low ionization energy) to steal a valence electron? – Harder with a higher ionization energy. More protons hold the electrons more tightly. 14

15. WWHS CHEMISTRY @WOODROWCHEM 15 Why isn’t the trend a straight line with a positive slope as the atomic number increases?