Section 7.7 Group Trends for the Active Metals

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Section 7.7Group 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

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Group 1A The Alkali MetalsCharacteristics

• 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 (oC) Density (g/cm2)
181 0.53
98 0.97
63 0.86
39 1.53
28 1.88
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Group 1A The Alkali MetalsChemical Reactions

• Hydrides
• 2M (s) H2(g) ? 2MH(s)
• Form hydrides
• In hydrides of alkali metals, hydrogen is
  present as H (hydride ion)
• Sulfides
• 2m(s) S(s) ? M2S(s)
• Form sulfides
• Water
• 2M(s) 2H2O(l) ? 2MOH(aq) H2(g)
• Vigorous reaction, very exothermic
• Heavier the metal, the more violent
  the reaction

Reaction of Potassium and Water
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Group 1A The Alkali MetalsChemical Reactions
(Continued)

• Oxygen (most complex)
• Lithium is the exception (reacts normally with O2
  )
• Sodium (Na) is the only alkali metal that forms
  metal peroxides , containing the O22- ion
• Reaction 2Na(s) O2(g) ? Na2O2(s)
• Potassium (K), Rubidium(Rb), and Cesium (Cs)
  react with Oxygen to form metal superoxides,
  containing the O2- ion
• Ex K(s) O2(g) ? KO2(s)

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Group 1A The Alkali MetalsInteresting 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
• Lithiums 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
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Alkali Metal Questions

• Predict the reactions of the following with
  oxygen
• Lithium
• Sodium
• Cesium

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Alkali Metal Answers

• 4Li(s) O2(g) ? 2Li2O(s)
• 2Na(s) O2(g) ? Na2O2(s)
• 3. Cs(s) O2(g) ? RbO2 (s)

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Group 2A The Alkaline Earth MetalsCharacteristic
s

• 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

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Group 2A The Alkaline Earth MetalsChemical
Reactions

• Trend of increasing reactivity within the
  Alkaline Earth Metals (Beryllium and Magnesium
  least, Strontium and Barium most)
• Shown by behavior of elements towards H2O (l and
  g)
• Beryllium doesnt react with water or steam, for
  example
• Magnesium doesnt react with water, but does
  react with steam
• Mg(s) H2O (g) ? MgO(s) H2 (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 H2
• Ex Ca(s) 2H2O(l) ? Ca(OH)2 (aq) H2(g)

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Group 2A The Alkaline Earth MetalsChemical
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) Cl21- (g) ? MgCl2(s)

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Group 2A The Alkaline Earth MetalsInteresting
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
• Strontiums most known or basic use is in
  fireworks

Strontium
Barium
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Alkaline Earth Metal Questions

• Why is calcium generally more reactive than
  magnesium?
• Why is calcium generally less reactive than
  potassium?

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Alkaline Earth Metal Answers

• 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.
• 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.

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Outside the Class

• Explosive Stuff (Alkali Metals)
• http//video.google.com/videoplay?docid-213426665
  4801392897eibfr2SsT1FoLIqQLzuLXhBgqalkalimeta
  lshlen
• Lithium in 7 Up

16
Works Cited

• Alkali Metals. Science Clarified. N.p., n.d.
  Web. 7 Nov. 2009. lthttp//www.scienceclarified.co
  m/?everyday/?Real-Life-Chemistry- Vol-1/?Alkali-Me
  tals.htmlgt.
• "Alkaline Earth Metals." Science Clarified. N.p.,
  n.d. Web. 7 Nov. 2009.       lthttp//www.sciencec
  larified.com/everyday/Real-Life-Chemistry-Vol- 1/ 
  Alkaline-Earth-Metals.htmlgt.
• 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. lthttp//www.chemicalelements.com/?groups/?a
  lkali.htmlgt.