1. Lab # 4

2. Key Terms Atomic Radius Ionization Energy Electronegativity Transition element Octet Rule Percent Composition

3. Electronegativity Vs. Ionization Energy Electronegativity - the attraction an atom has for its Valence electrons. Ionization energy - the amount of energy that is needed to remove an electron from its Valence shell. They both increase traveling across the table from left to right, and decrease traveling down the table.

4. Ionization energy and Electronegativity Ionization energy/ Electronegativity Increase

5. Atomic Radius atomic radius Increases going down Atomic radius decreases going to the right

6. Why is all this important? The larger the atomic radius, the farther the Valence electrons are from the nucleus. Thus the weaker the attraction between nucleus and the electrons. Thus the atom will loose its valence electrons easily. Thus the atom is: VERY REACTIVE !

7. Examples Which element has the higher I/E Lithium or Bromine? Bromine farther to the right. Which element has the higher I/E Lithium or Potassium? Lithium; higher on the table. Which element has the larger atomic radius Lithium or Bromine? Lithium; farther to the left Which element has the larger atomic radius Lithium or Potassium? Potassium; its lower on table

8. Group 2 metals Vs. Group 1 Group 1 metals are very reactive Group 2 metals are reactive, but not as much as group. Why ? Because the atomic radius is smaller; and because of a higher Electronegativity / Ionization energy. This trend continues across the table.

9. Atom Vs. Ion Atoms – No charge, unreactive, and listed on the periodic table. Ions – Have a charge, reactive and NOT LISTED on the periodic table. Atoms become ions by either gaining or loosing electrons. Metal atoms loose electrons to become ions and non metal atoms gain electrons to become ions

10. Potassium Large atomic radius and low electronegativity Potassium atom easily looses one electron to become an ion. Its easier and it take less energy for potassium to loose 1 then to try to gain 7 valence electrons. Group 1 metal Very Reactive

11. Chloride Chloride can easily gain 1 one electron to become an ion, but cannot loose 7 electrons. Why Chloride has a high electronegativity/ ionization energy, and the atomic radius is very small. In English (A very tight grip on the valence electrons) Group #7 Halides (salt formers) Non-metals very reactive

12. K + and Cl - reacting Since potassium easily looses 1 electron to become an ion, and since chloride easily gains 1 electron to become the chlorine ion we have: K +1 + Cl -1 → KCl Both have a charge → Both charges cancel out Ions have charges and compounds do not.

13. Today in lab: We are going to determine the amount of water that is present in a sample of salt. We will use percent composition.

14. Lab # 4 Wash your crucible and cover. Heat your crucible for 2 minutes using a Bunsen Burner Allow to cool for 5 minutes and weigh a crucible and cover. (Do not touch for two reasons) Determine the mass of the empty crucible and cover. Add the hydrated salt so that the crucible is ½ to ¾ full. Determine the mass of crucible, cover and salt. Heat, and allow to cool as directed in book. Reweigh crucible and sample

15. The mass of the dehydrated salt. Use a balance to obtain the mass of the dehydrated salt Where M = mass of

16. Percent composition Part over whole X 100 Ex#1 What percent of iron is present in a 55 gram sample that contains 22 grams of iron?

17. Due Next Week: Complete lab: pg 28 Complete homework and exercise for lab # 4 pgs 29-30