Summary of alkaline earth metals ......
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Alkaline Earth Metals
●Memebers of the group
-Group 2 of the periodic table consists of six elements:
1-Beryllium (Be)
2-Magnesium (Mg)
3-Clacium (Ca)
4-Strontium (Sr)
5-Radium (Ra)
Imp:-Radium is radioactive.
These elements are also called alkaline earth metals because the oxides of Mg,Ca,Sr and Ba are found in earth crust and are alkaline in mixture.
●General electronic configuration.
The general electronic configuration of alkaline earth metals is (noble gas) ns^2 where n=2-7.
●Atomic and ionic radii.
The atomic and ionic radii of alkaline earth metals are fairly large though smaller than those of the corresponding alkali metals.
●Ionization Enthalpy
The first and second ionization enthalpies of alkaline earth metals are fairly low; the second ionization enthalpy (∆iH2) being almost double of the first ionization enthalpy (∆iH1).
●Hydration Enthalpy
Like alkali metal ions, the hydration enthalpies of alkaline earth metal ions decrease as the size of the ion increases down the group, i.e., Be2+>Mg2+>Ca2+>Sr2+>Ba2+.
●Oxidation State.
All alkaline earth metals uniformly show an oxidation state of +2 both in the solid state or in aqueous solutions. In the solid state, the greater lattice enthalpy of the M2+ ions more than compensates the higher second ionization enthalpy while in the aqueous solution, it is the greater hydration enthalpy of the M2+ ions (relative to M+ ions) which more that compensates the higher second ionization enthalpy.
●Electropositive Character
Alkaline earth metals are strongly electropositive since they have a strong tendency to lose both the valence electrons to form M2+ ions having noble gas configuration. However, due to small size and higher ionization enthalpies, they are less electropositive than alkali metals. Further, the electropositive character increases down the group (i.e., Be<Mg<Ca<Sr<Ba) as the ionization enthalpies decrease.
●Melting and boiling points
The melting points and boiling points of alkaline earth metals are low but higher than those of alkali metals. However, down the group, the melting points and boiling points do not show any regular trend.
●Density
The alkaline earth metals are denser than the alkali metals due to smaller size and better packing of the atoms in the crystal lattice.
●Flame Colouration
Like alkali metals salts, alkaline earth metals and their salts also impart a characteristic colour to the flame.
Calcium-Brik red
Strontium-Crimson
Barium-Apple Green
Radium-Crimson
Be and Mg do not impart any colour to the flam.
●Reducing Character
The reducing character of alkaline earth metals increases down the group as the ionization enthalpy of the metals decreases or the electrode potential becomes more and more negative down the group.
●Action of air
Alkaline earth metals on heating in air form a mixture of oxides and nitrides.
2M+O2------2MO
●Action of water
The reactivity of alkaline earth metals towards increases down the group from Mg to Ba. Be does not react with hot water or even steam, Mg reacts with hot water but Ca, Sr and Ba react vigorously even with cold water evolving H2 gas.
●Action of hydrogen
All the alkaline earth metals except Be combine with hydrogen directly on heating to form metal hydrides (MH2)
●Action of Acids
Like alkali metals, alkaline earth metals also react with acids evolving H2 gas. Be, however, being amphoteric dissolves both in alkalies and acids liberating H2 gas.
●Action of halogens
When heated with halogens, all alkaline earth metals form halides of the general formula, MX2.
●Memebers of the group
-Group 2 of the periodic table consists of six elements:
1-Beryllium (Be)
2-Magnesium (Mg)
3-Clacium (Ca)
4-Strontium (Sr)
5-Radium (Ra)
Imp:-Radium is radioactive.
These elements are also called alkaline earth metals because the oxides of Mg,Ca,Sr and Ba are found in earth crust and are alkaline in mixture.
●General electronic configuration.
The general electronic configuration of alkaline earth metals is (noble gas) ns^2 where n=2-7.
●Atomic and ionic radii.
The atomic and ionic radii of alkaline earth metals are fairly large though smaller than those of the corresponding alkali metals.
●Ionization Enthalpy
The first and second ionization enthalpies of alkaline earth metals are fairly low; the second ionization enthalpy (∆iH2) being almost double of the first ionization enthalpy (∆iH1).
●Hydration Enthalpy
Like alkali metal ions, the hydration enthalpies of alkaline earth metal ions decrease as the size of the ion increases down the group, i.e., Be2+>Mg2+>Ca2+>Sr2+>Ba2+.
●Oxidation State.
All alkaline earth metals uniformly show an oxidation state of +2 both in the solid state or in aqueous solutions. In the solid state, the greater lattice enthalpy of the M2+ ions more than compensates the higher second ionization enthalpy while in the aqueous solution, it is the greater hydration enthalpy of the M2+ ions (relative to M+ ions) which more that compensates the higher second ionization enthalpy.
●Electropositive Character
Alkaline earth metals are strongly electropositive since they have a strong tendency to lose both the valence electrons to form M2+ ions having noble gas configuration. However, due to small size and higher ionization enthalpies, they are less electropositive than alkali metals. Further, the electropositive character increases down the group (i.e., Be<Mg<Ca<Sr<Ba) as the ionization enthalpies decrease.
●Melting and boiling points
The melting points and boiling points of alkaline earth metals are low but higher than those of alkali metals. However, down the group, the melting points and boiling points do not show any regular trend.
●Density
The alkaline earth metals are denser than the alkali metals due to smaller size and better packing of the atoms in the crystal lattice.
●Flame Colouration
Like alkali metals salts, alkaline earth metals and their salts also impart a characteristic colour to the flame.
Calcium-Brik red
Strontium-Crimson
Barium-Apple Green
Radium-Crimson
Be and Mg do not impart any colour to the flam.
●Reducing Character
The reducing character of alkaline earth metals increases down the group as the ionization enthalpy of the metals decreases or the electrode potential becomes more and more negative down the group.
●Action of air
Alkaline earth metals on heating in air form a mixture of oxides and nitrides.
2M+O2------2MO
●Action of water
The reactivity of alkaline earth metals towards increases down the group from Mg to Ba. Be does not react with hot water or even steam, Mg reacts with hot water but Ca, Sr and Ba react vigorously even with cold water evolving H2 gas.
●Action of hydrogen
All the alkaline earth metals except Be combine with hydrogen directly on heating to form metal hydrides (MH2)
●Action of Acids
Like alkali metals, alkaline earth metals also react with acids evolving H2 gas. Be, however, being amphoteric dissolves both in alkalies and acids liberating H2 gas.
●Action of halogens
When heated with halogens, all alkaline earth metals form halides of the general formula, MX2.
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o_o is this summary?
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it's ok.... ;)
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The alkaline earth metals are all of the elements in the second column (column 2A) of the periodic table. This group includes beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba) and radium (Ra). Alkaline earth metals have only two electrons in their outermost electron layer.
Alkaline earth metals get the name 'alkaline' because of the basic nature of the compounds they form when bonded with oxygen.
Properties and Characteristics
Alkaline earth metals in their pure forms are generally shiny and silvery. They rarely occur in their pure form, however, because they are very reactive. Alkaline earth metals have two electrons in their outermost electron layer, which take relatively little energy to remove. The energy it takes to remove an electron from an element is called the ionization energy. Alkaline earth metals have relatively low ionization energies for their first two electrons; because of this, alkaline earth metals exist with a 2+ charge most of the time. It is most common to find them in ionic compounds or as ions.
Alkaline earth metals get the name 'alkaline' because of the basic nature of the compounds they form when bonded with oxygen.
Properties and Characteristics
Alkaline earth metals in their pure forms are generally shiny and silvery. They rarely occur in their pure form, however, because they are very reactive. Alkaline earth metals have two electrons in their outermost electron layer, which take relatively little energy to remove. The energy it takes to remove an electron from an element is called the ionization energy. Alkaline earth metals have relatively low ionization energies for their first two electrons; because of this, alkaline earth metals exist with a 2+ charge most of the time. It is most common to find them in ionic compounds or as ions.
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