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Section 7.7 Group Trends for the Active Metals

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Title: Section 7.7 Group Trends for the Active Metals


1
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

3
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
4
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
5
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)

6
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
7
Alkali Metal Questions
  • Predict the reactions of the following with
    oxygen
  • Lithium
  • Sodium
  • Cesium

8
Alkali Metal Answers
  • 4Li(s) O2(g) ? 2Li2O(s)
  • 2Na(s) O2(g) ? Na2O2(s)
  • 3. Cs(s) O2(g) ? RbO2 (s)

9
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

10
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)

11
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)

12
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
13
Alkaline Earth Metal Questions
  • Why is calcium generally more reactive than
    magnesium?
  • Why is calcium generally less reactive than
    potassium?

14
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.

15
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.
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