Group Trends
 
 

1A

3  Li

11  Na

19  K

37  Rb

55  Cs

87  Fr

The word "alkali" is derived from an Arabic word meaning "ashes". Many sodium and postassium compounds were isolated from wood ashes (Na₂CO₃ and K₂CO₃ are still occasionally referred to as "soda ash" and "potash").
As we move down the group (from Li to Fr) we find the following trends:

• All have a single electron in an 's' valence orbital
• The melting points and heats of sublimation decreases going down the group.
• The density increases going down the group.
• lattice energies decreases going down the group.
• The atomic radius increases going down the group.
• The ionization energy decreases (first ionization energy) going down the group
• Effective hydrated radii and hydration energies decreases going down the group.

.

This represents the relative ease with which the lone electron in the outer 's' orbital can be removed.
The alkali metals are very reactive, readily losing 1 electron to form an ion with a 1+ charge:

Due to this reactivity, the alkali metals are found in nature only as compounds. The alkali metals combine directly with most nonmetals:

• React with hydrogen to form solid hydrides

• React with sulfur to form solid sulfides

• React with chlorine to form solid chlorides

• Alkali metals react with water to produce hydrogen gas and alkali metal hydroxides (very exothermic)

The reaction between alkali metals and oxygen is more complex:

• A common reaction is to form metal oxides which contain the O^2- ion

• Other alkali metals can form metal peroxides (contains O₂^2- ion)

• K, Rb and Cs can also form superoxides (O₂^- ion)

Solubility Rules
 

Negative Ions (Anions)	+	Positive Ions (Cations)	=	Solubility of compounds in water	Example
any anion	+	alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+)	=	soluble	sodium fluoride, NaF, is soluble
any anion	+	hydrogen ion [H+(aq)]	=	soluble	sodium hydride, NaH, is soluble
any anion	+	amonium ion (NH4+)	=	soluble	ammonium chloride, NH4Cl, is soluble
nitrate NO3-	+	any cation	=	soluble	potassium nitrate, KNO3, is soluble
acetate (CH3COO-)	+	any cation	=	soluble	sodium acetate, CH3COONa, is soluble
Chloride (Cl-), Bromide (Br-), Iodide (I-)	+	silver (Ag+), lead (Pb2+), mercury (Hg2+), copper (Cu+), thallium (Tl+)	=	low solubility (insoluble)	silver chloride, AgCl, forms a white precipitate (a white solid)
	+	any other cation	=	soluble	potassium bromide, KBr, is soluble
Suphate (SO42-)	+	calcium (Ca2+), strontium (Sr2+), barium (Ba2+), lead (Pb2+), radium (Ra2+)	=	low solubility (insoluble)	barium sulphate, BaSO4, forms a white precipitate (a white solid)
	+	any other cation	=	soluble	copper sulphate, CuSO4, is soluble
Sulfide S2-	+	alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), alkali earth metals (Be2+,Mg2+,Ca2+,Sr2+,Ba2+,Ra2+), and H+(aq), NH4+	=	soluble	magnesium sulfide, MgS, is soluble
	+	any other cation	=	low solubility (insoluble)	zinc sulfide, ZnS, is insoluble
Hydroxide OH-	+	alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+,Sr2+,Ba2+,Ra2+,Tl+	=	soluble	strontium hydroxide,  Sr(OH)2, is soluble
	+	any other cation	=	low solubility (insoluble)	silver hydroxide, AgOH, is insoluble (forms a precipitate)
Phosphate, PO43-, Carbonate, CO32-, sulphite, SO32-	+	alkali ions (Li+,Na+,K+,Rb+,Cs+,Fr+), H+(aq),NH4+	=	soluble	ammonium phosphate, (NH4)3PO4, is soluble
	+	any other cation	=	low solubility (insoluble)	magnesium carbonate, MgCO3, is insoluble

Flame Colors

SPECTRA OF  ALAKLI METAL SALTS (FLAME TEST)

APPARATUS:

• Spray units
• Salt solutions
• Bunsen burner

DIAGRAM: 

DESCRIPTION: The characteristic spectrum emitted by salts is easily demonstrated to a large audience by spraying a solution of the salt into the flame of a bunsen burner. For best results adjust the bunsen burner to give a large flame with little oxygen.

Salt solution available
Alkali metals

• Sodium chloride:  bright orange
• Potassium Nitrate:  lilac
• Lithium Chloride: crimson red
• Potassium Chloride: lilac

• Calcium chloride: brick red
• Strontium Nitrate: bright crimson red
• Strontium Chloride:bright crimson red
• Barium Nitrate: light green

• lead: blue/white

• Cupric Chloride: blue/green
• Cupric Nitrate: blue/green

• Lithium burns readily in air forming a mixture of lithium suboxide.

• Lithium reacts readily with the halogens, forming the appropriate lithium salt.

• Lithium reacts violently with water, forming lithium hydroxide and liberating hydrogen.

Metal-Ammonia Solutions

For over a hundred years, chemists have known about the unusual properties of solutions formed
when alkali metals -- the elements in the far left column of the periodic table -- dissolve in liquid
ammonia (NH3). "Since the early 1800s," says Klein, "the idea that ammonia could dissolve an
alkali metal and that the solution changes color has been well known. But it's only in the last 30
years that it's been the subject of more intense study."

At low concentrations, a metal-ammonia solution is blue, and it behaves like an electrolyte -- the
metal atoms lose one electron and become positively charged ions, and the free electrons in
solution act like negative ions. There is electrical conductivity, similar to salt in water or battery
acid, but the conductivity is more like an insulator than a metal.

At high concentrations, around 10 percent metal and higher, the solution changes to a
coppery-bronze color. Along with the color change comes a shift to the high electrical conductivity
of a liquid metal. How does the change occur? What exactly happens to shift the electronic state
from insulator to metal? Experiments have measured the change, and theorists have been able to
speculate about how it happens. Until recently, however, the computing power wasn't available to
provide detailed, quantitative understanding.
"How would you build these images of what's going on," says Klein, "without computers? The
problem just wasn't suited to be tackled. It's a complex problem, involving ions in solution and
electrons and the electronic states changing from localized to delocalized -- this is very tough to
describe by analytic theory."
Ammonium as a Pseudo-Alkali Metal Ion
Similarities Between Lithium and the Alkaline Earth Metals

Diagonal Relationships
     In addition to horizontal and vertical trends, there is a diagonal relationship between elements such as Li and  Mg, Be and Al, B and Si, that have an adjacent upper left/lower right relative location in the periodic table.   These pairs of elements have similar size and electronegativity, resulting in similar properties. Diagonally related pairs of elements show similar chemical properties. A nice way to see trends in radii for different oxidation states, groups and periods. Comparisons are quick and easy to make and the rotatability allows diagonal relationships to be observed.
Biological Aspects
Lithium: A Treatment For Manic Depression (Bipolar Disorder)
Manic depressive illness, known in medical communities as bipolar illness, is the most
distinct and dramatic of the depressive or affective disorders. Unlike major depression,
which occurs at any age, manic-depressive illness generally strikes before the age of 30.
Almost 2 million Americans suffer from bipolar illness.
The distinction between bipolar illness and other depressive disorders is that patients swing
from depression to mania, generally with periods of normal moods in between the two
extremes. Some patients, however, cycle from mania to depression and back within a few
days and without a period of normal mood. People with this condition are called rapid
cyclers.
Treatment
Many other physical and mental disorders can mimic manic-depressive illnesses. For
example, a person with symptoms of manic-depression could be reacting to substances
such as amphetamines or steroids or could suffer from an illness such as multiple
sclerosis. Anyone who has symptoms of bipolar disorder should receive a thorough and
complete medical evaluation to rule out any other mental or physical disorders and to ensure
accurate diagnosis and treatment.
Though manic-depressive disorder can become disabling, it also is among the most
treatable of the mental illnesses. The combination of psychotherapy and medications
returns the vast majority of manic-depressive patients to happy, functioning lives.
The most common medication, lithium carbonate, successfully reduces the number and
intensity of manic episodes for 70 percent of those who take the medication. Twenty percent
become completely free of symptoms. Those who respond to lithium best are patients who
have a family history of depressive illness and who have periods of relatively normal mood
between their manic depressive phases.
Very effective in treating the manic phase, lithium also appears to prevent repeated episodes
of depression. One theory for this is that in controlling the mania, lithium helps prevent the
swing into depression.
Lithium works by bringing various neurotransmitters in the brain into balance. Scientists
think the medication may affect the way or the speed at which the brain cells break down the
neurotransmitters that are thought to control moods.
However, like all medications, lithium can have side effects and must be very closely
monitored by a psychiatrist. The doctor should measure the level of lithium in the patient's
blood as well as how well the patient's kidneys and thyroid gland are working. Among the
side effects are weight gain, excessive thirst and urination, stomach and intestinal irritation,
hand tremors, and muscular weakness. More serious side effects are hypothyroidism,
kidney damage, confusion, delirium, serious seizures, coma and, in patients who aren't
closely monitored by a physician, even death.
However, properly monitored, lithium has returned thousands of people to happy, functioning
lives that would not be possible without medication. The complications of this disorder
include financial, social, family and occupational disintegration and suicide.
Generally, people in treatment for manic-depressive illness also receive psychotherapy. Like
all serious illnesses, manic-depressive disorders disrupt a person's relationships with
others, and can create poor self-esteem. Medications can control the symptoms, but
patients often also need to work out the side effects of the illness and to live with their new
range of emotions. This is where psychotherapy is needed. The patient can work with the
therapist in working out the problems created by the disorder and re-establishing the
relationships and healthy self-image that are shaken by the illness. In many cases, a patient
needs the therapist's support to ensure that he complies with his treatment.
Sodium/potassium Ion Pumps
The sodium/potassium pump is essential to the health of virtually every cell in all animals, including humans. Scientists at the MBL have spent years studying the molecular mechanisms by which this pump transports sodium and potassium ions across cellular membranes. They use the giant nerve cell of the Woods Hole squid (Loligo pealeii) as a model system for their research.

Recently, in the journal Nature, Miguel Holmgren, Jonathan Wagg, Francisco Bezanilla, Robert Rakowski, Paul De Weer, and David Gadsby, all summer investigators at the MBL, described their latest findings about how this microscopic molecular machine actually works.

“We already knew that this pump, which is a single protein molecule, transports three sodium ions across the cell membrane at once,” explains David Gadsby of The Rockefeller University in New York. “In this paper we show that three separate changes in the shape of the pump protein release the three sodium ions from the pump one at a time, in a fixed sequence.”

Gadsby says that this new information will help scientists understand in greater detail how these, and other, essential ion pumps perform the crucial work that keeps all our cells alive.
Element Reaction Flow-Chart
The Alkali and Alkaline Earth Metals
Are metals in the chemical sense but not in the  common sense, as most of them are hardly ever seen in  the metallic state.
 These two groups together constitute the s-block  elements.   The variations in properties among these elements  illustrate periodic trends.
The Alkali Metals

     Too easily oxidized to be found in free state and too
     difficult to reduce for common reducing agents to be
     effective.

     Pure metals obtained by electrolysis of their molten
     salts.

     K can also be obtained by exposing liquid KCl to
     sodium vapor.
Physical Properties of Group 1

     Silvery gray in pure state.

     Soft (Lithium, the hardest, is softer than lead.)

     Low melting points (See chart at left, where
     nu-merical values are in degrees Celsius.)

     Liquid metals used as coolants in breeder nuclear
     reactors.

Appearance of the Alkali Metals
     Lithium (left) and sodium (right) corrode rapidly in
     moist air. These surfaces have just been cut (easily
     done with a dull knife) and even so the shiny metallic
     luster is already disappearing.

Appearance of the Alkali Metals

     Potassium (left) and rubidium and cesium (right) are
     even more reactive. The last two have to be stored in
     sealed, airless containers. Francium has never been
     prepared in visible quantities.

Chemical Properties of Group 1

     Low first ionization energies mean that these elements
     usually found as singly charged cations

     Excellent reducing agents in metallic form

          Molten sodium is used to produce zirconium and titanium from their chlorides
          With strongly negative ionization potentials, alkalies can even reduce water.
               The vigor of this reaction increases going down the group.
               The higher densities of Rb and Cs mean H2 gas is formed under water, where
               it can create a shock wave.
(a) Lithium reacts fairly quietly with water.

     (a) Lithium reacts fairly quietly with water.

     (b) Sodium reaction produces enough heat to melt the
     metal, which then assumes a spherical shape.

     (c) Potassium generates so much heat that the
     hydrogen produced is ignited.
Oxides and Nitrides

     Products of reaction with oxygen vary going down the
     group

          Lithium forms mainly the oxide, Li2O
          Sodium forms predominately the peroxide, Na2O2
          Potassium forms the superoxide, KO2

     The difference is due to the greater stability of ionic
     compounds when cations and anions have similar
     radii.

     Only lithium directly forms a nitride, Li3N, when
     heated in air.
Products of alkali metals’ reactions with
oxygen

     Products of alkali metals’ reactions with oxygen

     Left, lithium oxide. Center, sodium peroxide. Right,
     potassium superoxide.

Some Important Compounds
    Sodium and potassium compounds are most common. Sodium compounds generally cheaper and more soluble; potassium compounds are less hygroscopic (water absorbing) and are a source of the potassium needed in fertilizer.
  NaCl is used in greater tonnage than H2SO4, but is not on list of “top chemicals” because it’s not manufactured.
 NaOH is base for production of other sodium salts.  Na₂SO₄, Na₂CO₃, NaHCO₃, KCl and KNO₃ are other much-used compounds
Uses of Some of the More “Exotic” Alkali
Metal Compounds
 Lithium carbonate is an effective treatment for  manic-depressive disorder.   Other lithium compounds are used in ceramics,    lubricants, and batteries.
Sodium azide, NaN3, is used in air bags.
Potassium: KO₂ is used in closed-system breathing apparatus to remove exhaled water vapor and generate oxygen gas.
 How do underwater rebreathers scrub CO₂ from air supplies?
Alkali metal hydroxides (column I and II metal hydroxides) can be used to absorb carbon dioxide (CO₂) in an enclosed atmosphere, like in a space craft or submarine. However, they're corrosive and absorb water vapor.
Is there any commonly-available material that is not toxic/dangerous that will absorb CO₂? (2) What is used in underwater rebreathers/CO₂-scrubbers?

  Plants absorb CO₂, of course, but they take up a lot of room  and are slow, inefficient CO₂ absorbers.  Most industrial CO₂ scrubbers use chemicals that don't meet your criteria. Monoethanolamine (MEA) is used to scrub carbon dioxide from gas streams, but it's corrosive and toxic in very small amounts. Ascarite II is a very efficient CO₂ absorbent, but it's basically nonfibrous asbestos covered with  sodium hydroxide.
           Potassium superoxide is an interesting possibility for spacecraft and submarine CO₂ scrubbing, since it regenerates oxygen as it reacts with carbon dioxide:
                                    4 KO₂(s) + 2 CO₂(g) = 2 K₂CO₃(s) + 3 O₂(g)
  But it isn't common, and it is quite toxic.   Calcium hydroxide (mixed with a small amount of sodium and potassium hydroxides) is used in most underwater rebreathers. The reaction between the hydroxides and CO₂ is exothermic, and divers can tell from the warmth of the scrubber canister that the absorption reaction is working. Failure of the canister lid can give the diver a mouthful of hydroxides- called a caustic cocktail in diving circles. It's apparently a memorable experience.
  You can learn more about the construction and chemistry of  rebreathers here.  The U. S. Department of Energy maintains a site on CO₂ removal technologies being considered to reduce global  carbon emissions.
Potassium hydroxide in Fuel Cells
Fuel cell  is an electric cell in which the chemical energy from the oxidation of  a gas fuel is converted directly to electrical energy in a continuous process (see oxidation and reduction). The efficiency of conversion from chemical to electrical energy in a fuel cell is between 65% and 80%, nearly twice that of the usual indirect method of conversion in which fuels are used to heat steam to turn a turbine connected to an electric generator. The earliest fuel cell, in which hydrogen and oxygen were combined to form water, was constructed in 1829 by the Englishman William Grove. In the hydrogen and oxygen fuel cell, hydrogen and oxygen gas are bubbled into separate compartments connected by a porous disk through which an electrolyte such as aqueous potassium hydroxide (KOH) can move. Inert graphite electrodes, mixed with a catalyst such as platinum, are dipped into each compartment.
     When the two electrodes are connected by a wire, the  combination of electrodes, wire, and electrolyte form a complete circuit, and an oxidation-reduction reaction takes place in the cell: hydrogen gas is oxidized to form water at the anode, or hydrogen electrode; electrons are liberated in this process and flow through the wire to the cathode, or oxygen electrode; and at the cathode the electrons combine with the oxygen gas and reduce it. The modern hydrogen-oxygen cell, operating at about 250&degC and a pressure of 50  atmospheres, gives a maximum voltage of about 1 volt. Fuel cells have been used to generate electricity in space flights.
ydrogen and the Alkali Metals

 Hydrogen isn't a metal, is it?
 No, it isn't; hydrogen itself is not considered to be one of the alkali metals. Its place in the table does make sense, though; hydrogen tends to behave like the other members of its column in chemical  reactions. For example, all these elements combine with oxygen to form compounds with the formula X₂O.   I'm not quite sure what you mean by X₂O.   X is a stand-in for the chemical symbol of any of  the elements in this column. In the case of hydrogen, the formula becomes H₂O, which of course is just water.     Later on, you'll see exactly why hydrogen belongs in this particular place in the periodic table.