1. Periodic Trends Elemental Properties and Patterns

2. Quick Write/ Warm Up 10/8 Give me a 2 minute reflection/writing on your weekend! Refreshing your memory: Draw the Cross and Dot diagram of an Oxygen atom. What is the electronic configuration of Oxygen?

3. The Periodic Law Atoms with similar properties appear in groups or families (vertical columns) on the periodic table. They are similar because they all have the same number of valence (outer shell) electrons, which determines their chemical behavior.

4. Metals, Nonmetals, Metalloids

5. TRENDS What trends do you notice in school? What trends do you follow in school? How is missing/ditching school a trend? What happens when you miss a day? What happens when you miss several days in a row?

6. Title these notes “Periodic Trends” Divide your notes into three sections: One titled “Atomic Radius” One titled “Ionization Energy” One titled “Electronegativity” As we go over these slides, add anything you think is important to those boxes.

7. Periodic Trends There are several important atomic characteristics that show predictable trends that you should know. The first and most important trend is atomic radius.

8. Atomic Radius Radius is the distance from the center of the nucleus to the “edge” of the electron cloud. measured in angstroms (Å). An angstrom is 1 x 10 -10 m.

9. Your turn Draw a simple cross dot diagram of the following atoms: Hydrogen Lithium Sodium Which group are these three elements in? What trend did you notice about these?

10. Atomic Radius The trend for atomic radius in a vertical column is to go from smaller at the top to larger at the bottom of the family. Why? With each step down the family, we add a new electron shell!

11. Atomic Radius The nucleus is more positive and the electron cloud is more negative as you move to the right (added protons and electrons because greater Atomic Number). The increased attraction pulls the cloud in, making atoms smaller as we move from left to right across a period.

12. Effective Nuclear Charge The pull of the positive protons in the nucleus on the electrons is called the Effective Nuclear Charge More Protons = More pull on electrons

13. Atomic Radius The overall trend in atomic radius looks like this.

14. Atomic Radius Here is an animation to explain the trend. On your help sheet, draw arrows like this:

15. Check for understanding What happens to atomic radius as you move DOWN a periodic table? Explain why! What happens to atomic radius as you move LEFT TO RIGHT on a periodic table? Explain why!

16. 1. Atomic Radius becomes larger. Because you add more electron shells to the electron cloud as you move down and make the distance between the nucleus and electron cloud edge larger! 2. Smaller because more electrons are attracted to the nucleus with more protons

17. Ionization Energy DO NOT WRITE THIS SLIDE. This is the second important periodic trend. If an electron is given enough energy (in the form of a photon) to overcome the effective nuclear charge holding the electron in the cloud, it can leave the atom completely. The atom has been “ionized” or charged. The number of protons and electrons is no longer equal.

18. Ionization Energy The energy required to remove an electron from an atom is ionization energy. (measured in kilojoules, kJ) The larger the atom is, the easier its electrons are to remove. Ionization energy and atomic radius are inversely proportional. Ionization energy is always endothermic, that is energy is added to the atom to remove the electron.

19. Ionization Energy

20. Ionization Energy How much energy needed to lose an electron Draw arrows on your help sheet like this:

21. Check for understanding What is ionization energy? How does the ionization energy of Francium (Fr) compare to Lithium (Li)?

22. Electronegativity Electronegativity is a measure of an atom’s attraction for another atom’s electrons. Generally, metals are electron givers and have low electronegativities. Nonmetals are electron takers and have high electronegativities.

23. Remember… These atoms give or take electrons to have a full outer shell!!!

24. Electronegativity Your help sheet should look like this: 0

25. Overall Reactivity This ties all the previous trends together in one package. However, we must treat metals and nonmetals separately. The most reactive metals are the largest since they are the best electron givers. The most reactive nonmetals are the smallest ones, the best electron takers.

26. Overall Reactivity Your help sheet will look like this: 0

27. Check for understanding **Think back to the video of the Alkali metals** Which metals are more reactive, the top of the periodic table metals or the bottom? Which non metals are more reactive?

28. The Octet Rule The “goal” of most atoms (except H, Li and Be) is to have an octet or group of 8 electrons in their valence energy level. They may accomplish this by either giving electrons away or taking them. Metals generally give electrons, nonmetals take them from other atoms. Atoms that have gained or lost electrons are called ions.

29. Ions When an atom gains an electron, it becomes negatively charged (more electrons than protons ) and is called an anion. In the same way that nonmetal atoms can gain electrons, metal atoms can lose electrons. They become positively charged cations.

30. Ions Here is a simple way to remember which is the cation and which the anion: This is a cat-ion. This is Ann Ion. He’s a “plussy” cat! She’s unhappy and negative. +

31. Ionic Radius Cations are always smaller than the original atom. The entire outer PEL is removed during ionization. Conversely, anions are always larger than the original atom. Electrons are added to the outer PEL.

32. Cation Formation 11p+ Na atom 1 valence electron Valence e- lost in ion formation Effective nuclear charge on remaining electrons increases. Remaining e- are pulled in closer to the nucleus. Ionic size decreases. Result: a smaller sodium cation, Na +

33. Anion Formation 17p+ Chlorine atom with 7 valence e- One e- is added to the outer shell. Effective nuclear charge is reduced and the e- cloud expands. A chloride ion is produced. It is larger than the original atom.