alkali metal

(noun)

Any of the soft, light, reactive metals of Group 1 of the periodic table; lithium, sodium, potassium, rubidium, cesium, and francium.

Related Terms

Examples of alkali metal in the following topics:

  • The Alkali Metals

    • Alkali metals are chemical elements from the s-block of the periodic table.
    • All the alkali metals react with water, with the heavier alkali metals reacting more vigorously than the lighter ones.
    • The pure alkali metal can also react directly with water.
    • All the discovered alkali metals occur in nature.
    • Most alkali metals have many different applications.

  • Strong Bases

    • Common examples of strong Arrhenius bases are the hydroxides of alkali metals and alkaline earth metals such as NaOH and Ca(OH)2.
    • The cations of these strong bases appear in the first and second groups of the periodic table (alkali and earth alkali metals).
    • Generally, the alkali metal bases are stronger than the alkaline earth metal bases, which are less soluble.
    • Usually, these bases are created by adding pure alkali metals in their neutral state, such as sodium, to the conjugate acid.

  • Anionic Chain-Growth Polymerization

    • Species that have been used to initiate anionic polymerization include alkali metals, alkali amides, alkyl lithiums and various electron sources.

  • Atomic Radius

    • Radii generally decrease from left to right along each period (row) of the table, from the alkali metals to the noble gases; radii increase down each group (column).
    • The radius increases sharply between the noble gas at the end of each period and the alkali metal at the beginning of the next period.
    • Therefore, the additional electron of next alkali metal (one row down on the periodic table) will go into a new outer shell, accounting for the sudden increase in the atomic radius.

  • Salt Formation

    • In the case of alkali metal hydroxides and simple amines (or ammonia) the resulting salts have pronounced ionic character and are usually soluble in water.
    • Heavy metals such as silver, mercury and lead form salts having more covalent character (3rd example), and the water solubility is reduced, especially for acids composed of four or more carbon atoms.

  • Binary Hydrides

    • Ionic, or saline, hydride is a hydrogen atom bound to an extremely electropositive metal, generally an alkali metal or an alkaline earth metal (for example, potassium hydride or KH).
    • Classical transition metal hydrides feature a single bond between the hydrogen center and the transition metal.
    • Interstitial hydrides most commonly exist within metals or alloys.
    • Their bonding is generally considered metallic.
    • Such bulk transition metals form interstitial binary hydrides when exposed to hydrogen.

  • Variation of Physical Properties Across a Period

    • For example, the alkali metals lie in one group (Group 1) and share similar properties, such as high reactivity and the tendency to lose one electron to arrive at a noble-gas electron configuration.
    • All Group 1 metals form halides that are white solids at room temperature.
    • All of the alkali halides and alkaline earth halides are solids at room temperature and have melting points in the hundreds of degrees centigrade.
    • In contrast, when an alkali halide or alkaline earth halide melts, the resulting liquid is an excellent electrical conductor.
    • This tells us that these molten compounds consist of ions, whereas the non-metal halides do not.

  • The Solubility of Amphoteric Metal Hydroxides

    • Amphoteric metal hydroxides behave as bases and acids, dissolving in excess alkali.
    • The oxides and hydroxides of the metals in Group 3 and higher tend to be weakly basic and mostly display an amphoteric nature.

  • Metallic Crystals

    • Metallic crystals are held together by metallic bonds, electrostatic interactions between cations and delocalized electrons.
    • These interactions are called metallic bonds.
    • Atoms in metals are arranged like closely-packed spheres, and two packing patterns are particularly common: body-centered cubic, wherein each metal is surrounded by eight equivalent metals, and face-centered cubic, in which the metals are surrounded by six neighboring atoms.
    • Some metals (the alkali and alkaline earth metals) have low density, low hardness, and low melting points.
    • The high density of most metals is due to the tightly packed crystal lattice of the metallic structure.

  • Carbides

    • They are generally prepared from metals or metal oxides at high temperatures (1500 °C or higher) by combining the metal with carbon.
    • Salt-like (saline) carbides are composed of the highly electropositive atoms, such as the alkali, alkali earth, and group-III metals, mixed with carbon.
    • Acetylides are formed from alkali, alkali earth, and lanthanoid metals with the acetylide anion C22-.
    • These carbides are metallic and refractory.
    • Metal complexes containing Cn fragments are well known.