Difference Between Alkali Metals and Alkaline Earth Metals

Alkali Metals vs Alkaline Earth Metals
 

As both Alkali metals and alkali earth metals are the first two groups in the periodic table, the difference between alkali metals and alkaline earth metals is a subject of interest for any chemistry student. Alkali metals and alkaline earth metals are also called the “S-block” elements because elements in both of these groups have their outermost electron(s) in the s-subshell.

Generally, we used the word “metal” for the materials that conduct electricity; both alkali metals and alkaline earth metals are good electrical and heat conductors. The elements in these two groups are the most reactive metals in the periodic table. Their melting points are relatively low compared to that of other metals. Alkali metals and alkaline earth metals have many similar properties, but this article discusses mainly their differences.

Difference Between Alkali Metals and Alkaline Earth Metals

What are Alkali Metals?

The alkali metals are the elements found in the first group of the periodic table. They are Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs) and Francium (Fr). They are all metals and very reactive and none of these metals do not occur as free metals in nature. Alkali metals are always stored in inert liquids such as kerosene because they rapidly react with the air, water vapour and oxygen in the air. Sometimes they explosively react with other substances. They can achieve the noble gas state easily, by removing the outermost electron in the valence shell.

The densities of Lithium and Sodium are less than the density of water. However, the other elements are denser than water. Many of alkali metal compounds (NaCl, KCl, Na2CO3, NaOH) are commercially very important.

What are Alkaline Earth Metals?

Alkaline earth metals are found in the second group of the periodic table. Group II elements include; Beryllium (Be), Magnesium (Mg), Calcium (Ca), Strontium (Sr), Barium (Ba) and Radium (Ra). Similar to alkaline metals, these elements also do not occur freely in the nature and they are also very reactive.

All the elements in this group are denser than water. Pure metals are silver-grey colored, but they tend to decolorize quickly when they are exposed to air because they form an oxide layer on the surface. Same as alkali metals, these metals are also good conductors in heat and electricity. All of the alkaline earth metals are commercially valuable.

What is the difference between Alkali Metals and Alkaline Earth Metals?

  • Electron configuration: Alkali metals have the electronic configuration of [Noble gas] ns1 and alkaline earth metals have, [Noble gas] ns2 electronic configuration.
  • Valence: All the alkali metals have an electron in their outermost shell and all the alkaline earth metals have two outer electrons. To achieve the noble gas configuration, alkali metals need to lose one electron (valence is “one”), whereas alkaline earth metals need to remove two electrons (valence is “two”).
  • Reactivity: Both alkali metals and alkaline metals are very reactive. Alkali metals are more reactive than alkaline earth metals.
  • Ionic charge: Alkali metals have +1 ionic charge in their compounds and alkaline earth metals have +2 ionic charge in compounds.
  • Hardness: Alkali metals are very soft and they can be cut with a sharp knife. Alkali earth metals are harder than the alkali metals.

Summary:

Alkali Metals vs Alkaline Earth Metals

Alkali metals and the alkaline earth metals are the group I and group II elements in the periodic table respectively. The most significant difference between these two groups is the electronic configuration. Group I elements have only one electron in the valence shell and group II elements have two electrons in their valence shell. These two groups have many similar properties as well as few differences. Both of these metals show only simple oxidation states and they have a fixed oxidation number in all chemical compounds. They are very reactive and do not freely occur in the nature.