The Properties Of Alkaline Earth Metal
The properties of alkaline earth metal that will be explained in this article is group trends, ionic character, ion hydration and solubility of alkaline earth metal salt. If you need this information, please read this article carefully.
Group Trends
The group trends of alkaline metal earth elements that we discuss here are magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Br).
Just like other metal, alkaline earth metal also has silvery looks in the surface. But this metal has fairly low density. Same with the alkali metal, the density of the alkaline metal earth is generally increase with increasing atomic number. Barium is the greater density of all alkaline metal earth elements.
The alkaline earth metals have stronger metallic bond than alkali metals elements. This is because the alkaline earth metal elements can be releasing more electron (2 electrons) in the metal crystal structure than alkali metal (1 electron).
We can see this stronger metallic bond from enthalpies of atomization of alkaline earth metal elements that significantly greater than alkali metal elements. This stronger metallic bond also reflected the higher melting points and hardness of the alkaline earth metal elements.
Although the density of the alkaline earth metal elements is increased down the group, the melting points and enthalpies of atomization of one atom are not had a really big difference with the others. Calcium has greater melting and enthalpies of atomization from all of the alkaline earth metal elements.
You can see the data from this table:
As we mentioned before, each atom of alkaline earth metal elements can release 2 electrons to form positive ion (+2). So because of that, the ionic radii of alkaline earth metal elements is smaller that alkali metal elements. The ionic radii also increase down the group.
The alkaline earth metal elements are less chemically reactive than alkali metal elements, but it is still more reactive than the other metallic elements in periodic table.
For examples :
All alkali metal elements are reacted vigorously with water producing a strong base solution and release hydrogen gas. But in alkaline earth metals, only calcium, strontium and barium can react with cold water.
Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)
The reactivity of alkaline earth metals is increasing down the group, so barium is most vigorously when reacting with water. They also produce a strong base solution and releases hydrogen gas.
Magnesium does not react with cold water, but it will react slowly with hot water.
All alkaline earth metal elements also react with many non-metal elements. For example, heated magnesium in chlorine gas will give magnesium chloride.
Mg(s) + Cl2(g) → MgCl2(s)
There is one specific property that only shown in alkaline earth metal elements, that is magnesium can react with nitrogen gas when it heating while other metal cannot react with nitrogen gas.
3Mg(s) + N2(g) → Mg3N2(s)
Ionic Character
The alkaline earth metal ions always have an oxidation number of +2 and their compounds are mainly stable, colorless and most of them are solid ionic substance. The bond in alkaline earth metal compounds is mostly ionic in character.
But magnesium and beryllium compounds show that the covalent character in their bond is greater than ionic character.
Ion Hydrations
Almost all salts of alkaline earth metal elements are hydrated in nature (hydrated means bind some water molecules in their crystal). For examples, calcium chloride can be found as the hexahydrate, tetrahydrate, dihydrate, and monohydrate.
But the salts of alkaline earth metals also exist in anhydrous form. As the charge density of the metals becomes smaller, so does the hydration number.
Group Trends
The group trends of alkaline metal earth elements that we discuss here are magnesium (Mg), calcium (Ca), strontium (Sr) and barium (Br).
Just like other metal, alkaline earth metal also has silvery looks in the surface. But this metal has fairly low density. Same with the alkali metal, the density of the alkaline metal earth is generally increase with increasing atomic number. Barium is the greater density of all alkaline metal earth elements.
The alkaline earth metals have stronger metallic bond than alkali metals elements. This is because the alkaline earth metal elements can be releasing more electron (2 electrons) in the metal crystal structure than alkali metal (1 electron).
We can see this stronger metallic bond from enthalpies of atomization of alkaline earth metal elements that significantly greater than alkali metal elements. This stronger metallic bond also reflected the higher melting points and hardness of the alkaline earth metal elements.
Although the density of the alkaline earth metal elements is increased down the group, the melting points and enthalpies of atomization of one atom are not had a really big difference with the others. Calcium has greater melting and enthalpies of atomization from all of the alkaline earth metal elements.
You can see the data from this table:
The alkaline earth metal elements are less chemically reactive than alkali metal elements, but it is still more reactive than the other metallic elements in periodic table.
For examples :
All alkali metal elements are reacted vigorously with water producing a strong base solution and release hydrogen gas. But in alkaline earth metals, only calcium, strontium and barium can react with cold water.
Ba(s) + 2H2O(l) → Ba(OH)2(aq) + H2(g)
The reactivity of alkaline earth metals is increasing down the group, so barium is most vigorously when reacting with water. They also produce a strong base solution and releases hydrogen gas.
Magnesium does not react with cold water, but it will react slowly with hot water.
All alkaline earth metal elements also react with many non-metal elements. For example, heated magnesium in chlorine gas will give magnesium chloride.
Mg(s) + Cl2(g) → MgCl2(s)
There is one specific property that only shown in alkaline earth metal elements, that is magnesium can react with nitrogen gas when it heating while other metal cannot react with nitrogen gas.
3Mg(s) + N2(g) → Mg3N2(s)
Ionic Character
The alkaline earth metal ions always have an oxidation number of +2 and their compounds are mainly stable, colorless and most of them are solid ionic substance. The bond in alkaline earth metal compounds is mostly ionic in character.
But magnesium and beryllium compounds show that the covalent character in their bond is greater than ionic character.
Ion Hydrations
Almost all salts of alkaline earth metal elements are hydrated in nature (hydrated means bind some water molecules in their crystal). For examples, calcium chloride can be found as the hexahydrate, tetrahydrate, dihydrate, and monohydrate.
But the salts of alkaline earth metals also exist in anhydrous form. As the charge density of the metals becomes smaller, so does the hydration number.
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