1. Section 7.7 Group Trends for the Active Metals Louis Wilkerson Andrew Katsman Michael Levin

2. Overview Group 1A: The Alkali Metals –Basic characteristics –Chemical Reactions Involving Alkali Metals –Interesting Facts Group 2A: The Alkaline Earth Metals –Basic characteristics –Chemical Reactions Involving Alkali Metals –Interesting Facts Outside the Class

3. Group 1A: The Alkali Metals Characteristics Soft metallic solids w/ silvery luster High thermal and electrical conductivities Very reactive Pattern: melting points decrease, first ionization energies decrease, and densities increase with the increase of the atomic radius Exist in nature only as compounds Combine directly with most nonmetals – (ex: Hydrogen and Sulfur) Melting Pt ( o C) | Density (g/cm 2 ) 1810.53 980.97 630.86 391.53 281.88

4. Group 1A: The Alkali Metals Chemical Reactions Hydrides: – 2M (s) + H 2 (g)  2MH(s) Form hydrides  In hydrides of alkali metals, hydrogen is present as H – (hydride ion) Sulfides – 2m(s) + S(s)  M 2 S(s) Form sulfides Water – 2M(s) + 2H 2 O(l)  2MOH(aq) + H 2 (g) Vigorous reaction, very exothermic Heavier the metal, the more violent the reaction Reaction of Potassium and Water

5. Group 1A: The Alkali Metals Chemical Reactions (Continued) Oxygen (most complex) – Lithium is the exception (reacts normally with O 2 – ) – Sodium (Na) is the only alkali metal that forms metal peroxides, containing the O 2 2- ion Reaction: 2Na(s) + O 2 (g)  Na 2 O 2 (s) – Potassium (K), Rubidium(Rb), and Cesium (Cs) react with Oxygen to form metal superoxides, containing the O 2 - ion Ex: K(s) + O 2 (g)  KO 2 (s)

6. Group 1A: The Alkali Metals Interesting Facts Alkali metals emit characteristic colors when placed in a flame – The high temperature of the flame electronically excites valence electron – Atom emits energy in the form of visible light as it returns to its ground state Sodium: – Table salt – Human Diet Lithium’s most-know or best purpose is a medication for people with bipolar disorder – THIS DOES NOT MEAN YOU SHOULD LICK A LITHIUM BATTERY TO CALM YOURSELF! People have actually tried this Potassium Lithium

7. Alkali Metal Questions Predict the reactions of the following with oxygen 1.Lithium 2.Sodium 3.Cesium

8. Alkali Metal Answers 1.4Li(s) + O 2 (g)  2Li 2 O(s) 2.2Na(s) + O 2 (g)  Na 2 O 2 (s) 3. Cs(s) + O 2 (g)  RbO 2 (s)

9. Group 2A: The Alkaline Earth Metals Characteristics Have typical metallic properties Alkaline Earth metals are harder and more dense than the Alkali metals Melt at higher temperatures than Alkali metals Do not have a distinct Periodic-Table-pattern Also, these are less reactive than the Alkali metals – Beryllium (Be) and Magnesium (Mg) are the least reactive of all the Alkaline Earth metals

10. Group 2A: The Alkaline Earth Metals Chemical Reactions Trend of increasing reactivity within the Alkaline Earth Metals (Beryllium and Magnesium least, Strontium and Barium most) – Shown by behavior of elements towards H 2 O (l and g) Beryllium doesn’t react with water or steam, for example Magnesium doesn’t react with water, but does react with steam – Mg(s) + H 2 O (g)  MgO(s) + H 2 (g) – Calcium and elements below react readily with water at room temperature However, more slow than alkali metals adjacent to them Produce the metal hydroxide and H 2 Ex: Ca(s) + 2H 2 O(l)  Ca(OH) 2 (aq) + H 2 (g)

11. Group 2A: The Alkaline Earth Metals Chemical Reactions (Continued) In Alkaline Earth metals, it is important to note that they have the tendency to lose their two outer s sublevel electrons in order to form 2+ ions – Example: Mg 2+ (s) + Cl 2 1- (g)  MgCl 2 (s)

12. Group 2A: The Alkaline Earth Metals Interesting Facts Like the Alkali metals, Alkaline Earth metal ions give off characteristic colors when strongly heated in a flame Both Magnesium and Calcium are used in: – Building and other structural applications – Dietary supplements – The metabolism of living things (including humans) Barium and Beryllium are very useful, for they are used in the areas of both medicine and jewelry, among other things Strontium’s most known or basic use is in fireworks Strontium Barium

13. Alkaline Earth Metal Questions 1.Why is calcium generally more reactive than magnesium? 2.Why is calcium generally less reactive than potassium?

14. Alkaline Earth Metal Answers 1.Why is calcium generally more reactive than magnesium? – As proved by the basic behaviors of alkaline earth metals with water, magnesium will only react only with steam. Calcium, however, reacts with both steam AND water. 2.Why is calcium generally less reactive than potassium? – Potassium has less valence electrons than calcium does. Thus, potassium is “more willing” to react than calcium. Also, alkaline earth metals are generally less reactive than their alkali metal counterparts.

15. Outside the Class Explosive Stuff (Alkali Metals): http://video.google.com/videoplay?docid=- 2134266654801392897&ei=bfr2SsT1FoLIqQLz uLXhBg&q=alkali+metals&hl=en# http://video.google.com/videoplay?docid=- 2134266654801392897&ei=bfr2SsT1FoLIqQLz uLXhBg&q=alkali+metals&hl=en# Lithium in 7 Up…

16. Works Cited “Alkali Metals.” Science Clarified. N.p., n.d. Web. 7 Nov. 2009.. "Alkaline Earth Metals." Science Clarified. N.p., n.d. Web. 7 Nov. 2009.. Brown, Theodore L., H. Eugene LeMay, Jr., and Bruce E. Bursten. “Chapter 7: Periodic Properties of the Elements.” Chemistry: The Central Science. 9th ed. Upper Saddle River, New Jersey: Prentice Hall, 2003. 236 - 273. Print. “Periodic Table: Alkali Metals.” ChemicalElements.com. N.p., n.d. Web. 7 Nov. 2009..