<< Chapter < Page Chapter >> Page >

Group 1: the alkali metals

The alkali metals lithium, sodium, potassium, rubidium, cesium, and francium constitute group 1 of the periodic table. Although hydrogen is in group 1 (and also in group 17), it is a nonmetal and deserves separate consideration later in this chapter. The name alkali metal is in reference to the fact that these metals and their oxides react with water to form very basic (alkaline) solutions.

The properties of the alkali metals are similar to each other as expected for elements in the same family. The alkali metals have the largest atomic radii and the lowest first ionization energy in their periods. This combination makes it very easy to remove the single electron in the outermost (valence) shell of each. The easy loss of this valence electron means that these metals readily form stable cations with a charge of 1+. Their reactivity increases with increasing atomic number due to the ease of losing the lone valence electron (decreasing ionization energy). Since oxidation is so easy, the reverse, reduction, is difficult, which explains why it is hard to isolate the elements. The solid alkali metals are very soft; lithium, shown in [link] , has the lowest density of any metal (0.5 g/cm 3 ).

The alkali metals all react vigorously with water to form hydrogen gas and a basic solution of the metal hydroxide. This means they are easier to oxidize than is hydrogen. As an example, the reaction of lithium with water is:

2Li ( s ) + 2H 2 O ( l ) 2LiOH ( a q ) + H 2 ( g )
A glass container that is half filled with a colorless liquid is shown. Blocks of a shiny silver solid float on top of the liquid in the container.
Lithium floats in paraffin oil because its density is less than the density of paraffin oil.

Alkali metals react directly with all the nonmetals (except the noble gases) to yield binary ionic compounds containing 1+ metal ions. These metals are so reactive that it is necessary to avoid contact with both moisture and oxygen in the air. Therefore, they are stored in sealed containers under mineral oil, as shown in [link] , to prevent contact with air and moisture. The pure metals never exist free (uncombined) in nature due to their high reactivity. In addition, this high reactivity makes it necessary to prepare the metals by electrolysis of alkali metal compounds.

A sealed, tube-like glass container is shown. The container is partially filled with a colorless liquid and contains two metallic spheres.
To prevent contact with air and water, potassium for laboratory use comes as sticks or beads stored under kerosene or mineral oil, or in sealed containers. (credit: http://images-of-elements.com/potassium.php)

Unlike many other metals, the reactivity and softness of the alkali metals make these metals unsuitable for structural applications. However, there are applications where the reactivity of the alkali metals is an advantage. For example, the production of metals such as titanium and zirconium relies, in part, on the ability of sodium to reduce compounds of these metals. The manufacture of many organic compounds, including certain dyes, drugs, and perfumes, utilizes reduction by lithium or sodium.

Sodium and its compounds impart a bright yellow color to a flame, as seen in [link] . Passing an electrical discharge through sodium vapor also produces this color. In both cases, this is an example of an emission spectrum as discussed in the chapter on electronic structure. Streetlights sometime employ sodium vapor lights because the sodium vapor penetrates fog better than most other light. This is because the fog does not scatter yellow light as much as it scatters white light. The other alkali metals and their salts also impart color to a flame. Lithium creates a bright, crimson color, whereas the others create a pale, violet color.

Questions & Answers

what is periodic chemistry
Joseph Reply
Le chatelier's principle
Adepoju Reply
how many isotopes does hydrogen have
Faith Reply
3 isotopes
FLIMZEE
3 isotopes
FLIMZEE
an lmportant medical use of nuclear radiation is
Faith Reply
the minimum amount of energy required for effective collosion btw reacting particle is known as
Faith
the minimum amount of energy required for effective collosion btw reacting particle is known as
Faith
hi
Best
hmmmmm
Aniebiet
the minimum amount of energy required for effective collosion btw reacting particle is known as
Faith
Hey
Faith
hi
Nag
how do I get MCQs and essay to work?
Jake Reply
I want spectroscopy
Nipun
Check on play store Maybe you'll get an app for that
Idrissa
what is electrolysis
lola Reply
state the periodic law
Kelly Reply
the modern periodic state dat element are arranged in row and column according to their atomic number
lola
what is chemistry
sullayman Reply
chemistry is the brach of science which deal with composition and dicomposion of matter
ezekier
What are the branchs of chemistry
Blessing
What is matter
Believe Reply
matter is anything that has mass or weight and accopies space
ezekier
what is endothermic
Yemi Reply
something that absorbs some form energy
mohammed
What is gas law
Clement Reply
law is the rule of government
Dawite
gas law I have no idea
Israel
There are different Gas Laws There's boyles law, Charles law... Etc
Kanji
can you be more specific
Allyson
wat is hydroxyl
James
why is borontrihydride considered a Lewis acid
Mmesoma Reply
electronic configuration
Elabo Reply
What is chemistry
Blessing Reply
it's is a branch of science that deals with the nature and composition of various matters and how the under go changes
Kelly
Pls what is the structural formula for propanonitrile
Olaiya Reply
chemistry is the study of the interaction, structure and properties of matter
Olaiya
If a man has a mass of 115 pounds,what is his mass in gram lb=453.6g?
Henok
Practice Key Terms 8

Get the best Chemistry course in your pocket!





Source:  OpenStax, Chemistry. OpenStax CNX. May 20, 2015 Download for free at http://legacy.cnx.org/content/col11760/1.9
Google Play and the Google Play logo are trademarks of Google Inc.

Notification Switch

Would you like to follow the 'Chemistry' conversation and receive update notifications?

Ask