Transcript Chemistry: McMurry and Fay, 5th Edition

Octet Rule (not law)
and Alkali Metals
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 1/1
The Octet Rule
Octet Rule: Main-group elements tend to undergo
reactions that leave them with eight outer-shell
electrons.
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/10
The Octet Rule
Octet Rule: Main-group elements tend to undergo
reactions that leave them with eight outer-shell
electrons.
Metals tend to have low Ei and low Eea.
They tend to lose one or more electrons.
Nonmetals tend to have high Ei and high Eea.
They tend to gain one or more electrons.
This is a rule, not a law!
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/11
The Octet Rule
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/12
Chemistry of the Group 1A
Elements: Alkali Metals
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•
Powerful reducing agents
Metallic
Bright, silvery
Malleable
•
•
•
•
Good conductors of electricity
Relatively soft
Very reactive
Occur only in salts
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/17
Chemistry of the Group 1A
Elements: Alkali Metals
Production
2LiCl(l)
2NaCl(l)
Electrolysis in KCl
450 °C
Electrolysis in CaCl2
580 °C
2Li(l) + Cl2(g)
2Na(l) + Cl2(g)
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Chapter 6/18
Chemistry of the Group 1A
Elements: Alkali Metals
Production
850 °C
KCl(l) + Na(l)
K(g) + NaCl(l)
750 °C
2RbCl(l) + Ca(l)
2Rb(g) + CaCl2(l)
750 °C
2CsCl(l) + Ca(l)
2Cs(g) + CaCl2(l)
Does this jive with the activity series? Na reducing K+?
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/19
Chemistry of the Group 1A
Elements: Alkali Metals
Reaction with Halogens
2M(s) + X2
2MX(s)
Rapidly form metal halides
M = Li, Na, K, Rb, or Cs
X = F, Cl, Br, or I
Reaction with Hydrogen and Nitrogen
Heat
2M(s) + H2(g)
M = Li, Na, K, Rb, or Cs
2MH(s)
Not so rapidly forms metal hydrides
Heat
6Li(s) + N2(g)
2Li3N(s)
Only lithium forms nitride
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Chapter 6/20
Chemistry of the Group 1A
Elements: Alkali Metals
Reaction with Oxygen
4Li(s) + O2(g)
2Li2O(s)
oxide
2Na(s) + O2(g)
Na2O2(s)
peroxide
KO2(s)
superoxide
K(s) + O2(g)
KO2 valuable in spacecraft and breathing devices
To remove water and carbon dioxide and give off
oxygen
Oxidation number of O?
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/21
Chemistry of the Group 1A
Elements: Alkali Metals
Reaction with Water
2M(s) + 2H2O(l)
2M1+(aq) + 2OH1-(aq) + H2(g)
M = Li, Na, K, Rb, or Cs
Reaction with Ammonia
2M(s) + 2NH3(l)
2M1+(soln) + 2NH21-(soln) + H2(g)
M = Li, Na, K, Rb, or Cs
Copyright © 2008 Pearson Prentice Hall, Inc.
Chapter 6/22
H26 – C6
• 6.14 – 6.17, 6.75, 6.87*, 6.89, 6.115*
6.115 – Li3N + H2O → NH3 + LiOH
LiO2 + H2O → LiOH