Periodic Properties: Groups I and II Group I—The Alkali Metals
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Periodic Properties: Groups I and II A. Group I—The Alkali Metals 1. Elements and Symbols Ion. Energy(kJ/mol) 2 nd Ion. En. a. Li = Lithium 520 7300 b. Na = Sodium 495 4560 c. K = Potassium 419 3052 d. Rb = Rubidium 403 2633 e. Cs = Cesium 376 2230 2. Reactivity with water a. These elements need to lose 1 e - to be like a Noble Gas b. Losing electrons is called “oxidation” c. Water can gain electrons (“reduction”) d. 2 M 0 (s) + 2 H 2 O(l) ------> 2 MOH(aq) + H 2 (g) e. Example: 2 Na 0 (s) + 2 H 2 O(l) ------> 2 NaOH(aq) + H 2 (g) f. Reactions are violently exothermic g. Basic solutions are formed
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Periodic Properties: Groups I and II Group I—The Alkali Metals Elements and SymbolsIon. Energy(kJ/mol) 2 nd Ion. En. Li = Lithium5207300 Na = Sodium4954560 K = Potassium 4193052 Rb = Rubidium4032633 Cs = Cesium3762230 Reactivity with water - PowerPoint PPT Presentation
Transcript of Periodic Properties: Groups I and II Group I—The Alkali Metals
Periodic Properties: Groups I and IIA. Group I—The Alkali Metals
1. Elements and Symbols Ion. Energy(kJ/mol) 2nd Ion. En. a. Li = Lithium 520 7300b. Na = Sodium 495 4560c. K = Potassium 419 3052d. Rb = Rubidium 403 2633e. Cs = Cesium 376 2230
2. Reactivity with watera. These elements need to lose 1 e- to be like a Noble Gasb. Losing electrons is called “oxidation”c. Water can gain electrons (“reduction”)d. 2 M0(s) + 2 H2O(l) ------> 2 MOH(aq) + H2(g)
e. Example: 2 Na0(s) + 2 H2O(l) ------> 2 NaOH(aq) + H2(g)
f. Reactions are violently exothermicg. Basic solutions are formed
Sodium metal reacting with water
3. Reactions with Oxygena. 4Li + O2 2Li2O Lithium Oxide [O2- is called oxide;]
b. 2Na + O2 Na2O2 Sodium Peroxide [O22- is called
peroxide]c. K + O2 KO2 Potassium Superoxide [O2
- is called superoxide]
d. Rb + O2 RbO2 Rubidium Superoxidee. Cs + O2 CsO2 Cesium Superoxide
B. Group II—The Alkaline Earth Metals1. Elements and Symbols Ion. Energy(kJ/mol) 2nd Ion. En.
a. Be = Beryllium 900 1757b. Mg = Magnesium738 1450c. Ca = Calcium 590 1145d. Sr = Strontium 550 1064e. Ba = Barium 503 965
2. Reactions with Oxygena. Much more predictable: 2 M0(s) + O2(g) ------> 2 MO(s)
b. 2 Ca0(s) + O2(g) ------> 2 CaO(s)
3. Reactivity with water• These elements need to lose 2 e- to be like a Noble Gas• M0(s) + 2 H2O(l) ------> M(OH)2(aq) + H2(g)• Example: Mg0(s) + 2 H2O(l) ------> Mg(OH)2(aq) + H2(g)• Reactions are slow, with some bubbling visible• Basic solutions are formed
4. Reactivity with Acida. M0(s) + 2 HCl(aq) ------> 2 MCl2(aq) + H2(g)b. Mg0(s) + 2 HCl(aq) ------> 2 MgCl2(aq) + H2(g)
C. Ionization Energy1. The energy required to remove an e- from a gaseous element2. X(g) + I.E. ------> X+(g) + e- 3. More reactive metals have lower Ionization Energies4. Ionization Energy decreases down a Group—the electron being removed
is farther from the nucleus, thus easier to remove5. Ca (I.E. = 590 kJ/mol) is more reactive than Mg (I.E. = 738 kJ/mol)6. K (I.E. = 419 kJ/mol) is more reactive than Li (I.E. = 520 kJ/mol)
Calcium Metal Reacting with Water to Form Bubbles of Hydrogen Gas
D. Metal Oxides and Water1. The Alkali and Alkaline Earth Metals react with water to make it basic2. 2 Na0(s) + 2 H2O(l) ------> 2 NaOH(aq) + H2(g)
3. Mg0(s) + 2 H2O(l) ------> Mg(OH)2(aq) + H2(g)
4. The oxides of these metals also react with water to make basic solutions5. 2KO2(s) + 2H2O(l) ------> 2KOH(aq) + O2(g) + H2O2(aq)
6. MgO(s) + H2O(l) ------> Mg(OH)2(aq)
E. Notes on Today’s Lab1. Do the reactions in the hood: H2 is produced
2. Do Part A first (metal hardness); then use same piece for Part B (H2O rxn)
DON’T THROW METALS IN TRASH: THEY CAN CATCH ON FIRE2 M0(s) + 2 ROH(l) ------> 2 M+OR-(aq) + H2(g)
3. Use the Bunsen burner in the hood to burn the Magnesium4. Phenolpthalein is red under basic conditions5. Orange pH paper turns blue under basic conditions
Incident: Sodium Metal-Solvent Fire
