1. Section 3 Representative Groups

2. Key Concepts Why do the elements in a group have similar properties? What are some properties of the A groups in the periodic table?

3. Valence Electrons A valence electron is an electron that is in the highest occupied energy level of an atom. Elements in a group have similar properties because they have the same number of valence electrons. These properties will not be identical because the valence electrons are in different energy levels.

4. Family 1 – The Alkali Metals

5. The Alkali Metals One valence electron in the outermost energy level Tend to lose the electron True metals Very reactive, never found un-reacted in nature Not many uses, but their compounds are needed for life Ex. NaCl 3 Li Lithium 11 Na Sodium 19 K Potassium 37 Rb Rubidium 55 Cs Cesium 87 Fr Francium

6. Family 2 – Alkaline Earth Metals

7. Alkaline Earth Metals Two valence electrons in their outermost energy level Tend to lose these electrons (true metals) Very reactive, never found un-reacted in nature (not as reactive as Alkali Metals because these have to lose two electrons) The compounds of these metals are very important Ex. Calcium compounds 4 Be Beryllium 12 Mg Magnesium 20 Ca Calcium 38 Sr Strontium 56 Ba Barium 88 Ra Radium

8. Transition Metals

9. Most have 1 or 2 valence electrons Properties similar to other metals Can share electrons as well as give them Usually bright colors (used in paints) Ex, Iron, Copper, Silver, Gold

10. Boron Family

11. 3 valence electrons Boron is a metalloid all others are metals Many uses for these elements Aluminum is the most abundant metal in Earth’s crust. 5 B Boron 13 Al Aluminum 31 Ga Gallium 49 In Indium 81 Tl Thallium

12. Carbon Family

13. 4 valence electrons Can either give or take 4 electrons or share electrons Can form millions of different compounds Carbon is a nonmetal, Silicon and Germanium are metalloids, the rest are metals Except for water, most of the compounds in your body contain carbon. 6 C Carbon 14 Si Silicon 32 Ge Germanium 50 Sn Tin 82 Pb Lead

14. Nitrogen Family

15. 5 valence electrons Tend to share electrons when bonding N and P are nonmetals, As and Sb are metalloids, and Bi is a metal Besides nitrogen, fertilizers often contain phosphorus. 7 N Nitrogen 15 P Phosphorus 33 As Arsenic 51 Sb Antimony 83 Bi Bismuth

16. Oxygen Family

17. 6 valence electrons Most share electrons in bonding O, S, and Se are nonmetals, Te and Po are metalloids Oxygen is the most abundant element in Earth’s crust. 8 O Oxygen 16 S Sulfur 34 Se Selenium 52 Te Tellurium 84 Po Polonium

18. Family 17 - Halogens

19. Halogens 7 valence electrons Most reactive nonmetals Need to gain only one electron to fill their outermost energy level Never found un-reactive in nature F most reactive nonmetal Fluorine and chlorine are gases, bromine is a liquid that evaporates quickly, and iodine is a solid that sublimes. Despite their physical differences, the halogens have similar chemical properties 9 F Fluorine 17 Cl Chlorine 35 Br Bromine 53 I Iodine 85 At Astatine

20. Family 18 – Noble Gases

21. Noble Gases The noble gases are colorless and odorless and extremely unreactive. Non-reactive gases Have a full outer energy level Most all other elements try to get their outer energy level to look like Noble Gases They need to bond with other elements to achieve this 2 He Helium 10 Ne Neon 18 Ar Argon 36 Kr Krypton 54 Xe Xenon 86 Rn Radon

22. Reviewing Concepts 1. Explain why elements in a group have similar properties. 2. What is the relationship between an alkali metal’s location in Group 1A and its reactivity? 3. What element exists in almost every compound in your body? 4. Which Group 5A elements are found in fertilizer? 5. Which group of elements is the least reactive? 6. Why is hydrogen located in a group with reactive metals?