All the alkaline earth metals like Beryllium, Magnesium, Calcium, Barium, Radium and Strontium have tow electrons in their outermost, s-orbital, i.e. all these elements have ns2 configuration. Since all the alkaline earth metal possess identical ns2 configuration, these elements resemble closely in the physical and chemical properties. For example all these elements:
Are good conductors (are metals)
Are good reducing elements
Exhibit valency of +2
Have a tendency to form ionic compounds by losing 2 electrons, and
Have a strong electropositive character.
Properties of Alkaline Earth Metal
The general trends in the physical properties of alkaline earth metal are as follows:
Atom and Ionic Radii – atoms of the alkaline earth metals have large size. Even the size of the +2 ions formed by the loss of two s-electrons is quite large. However, the size of the alkaline earth metals and their +2 ions is small as compared to the corresponding alkali metals and their +1 ion. His is because of the increased nuclear charges in case of the alkaline earth metals and their+2 ions.
Ionization Potential – on account, of large atomic size, the outermost electron in an alkaline earth metal is loosely held. Consequently, alkaline earth metals have low ionization potentials. Alkaline earth metals have smaller size and greater value of value as nuclear charge as compared to the corresponding alkali metals. Therefore, the electrons in alkaline earth metals are more firmly held than in the alkali metals. Hence, ionization energy of alkaline earth metals is greater than the corresponding alkali metal.
Oxidation State or Valence – due to their low ionization energies, alkaline earth metals can readily lose two s-electrons from the outermost orbit. Hence, these metals form bivalent positive ions. Biovalent positive ions of alkaline earth metals are stable than +1 ions, although more energy is required to charge +1 ions into +2 ions. This is because +2 ions are heavily hydrated.
Electropositive or Metallic character – the alkaline earth metals have a high tendency to lose the electrons due to their low I.P. values. Consequently, these are strongly electropositive or metallic in nature. Since, alkaline earth metals have higher ionization energies, they have fewer tendencies to lose electrons and for this reason they are less electropositive than alkali metals.
Electro-negativity – due to their strong electro-positive character, alkaline earth metals have a very little tendency to attract electrons. Therefore, they have a very low electro-negativity value.
Electron Affinity – due to their stable configurations, alkaline earth metals have a very little tendency to gain electrons. Therefore, they have very low electron affinity values.
Ionic Compound Formation – since, these electrons are highly electropositive, they readily react with highly electronegative elements by transfer of their valence electrons. Therefore, compound formed are ionic in nature.
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