Group 2 Elements: Alkaline Earth Metals
Table of Content
- Define Alkaline Earth Metals
- Physical properties of Alkaline Earth Metals
- Chemical properties of Alkaline Earth Metals
- Uses of Alkaline Earth Metals
Group 2 elements are known as Alkaline Earth Metals. It includes beryllium, magnesium, calcium, strontium, barium, and radium. The most common oxidation state found is +2. The electronic configuration of alkaline earth metals are as follows:
Fig. 1. Electronic configuration, symbol, atomic number of alkaline earth metals
The atomic and ionic radii of alkaline earth metals are smaller than those of alkali earth metals due to increase in effective nuclear charge from left to right in a period. But as one moves from top to bottom in a group atomic radii and ionic radii increases.
Fig. 2. Location of alkaline earth metals in periodic table
Alkaline earth metals have lower ionization enthalpies due to large sizes. As we move from beryllium to radium, size increases so ionization enthalpy decreases. Their first ionization enthalpy is higher than their second ionization enthalpy.
Hydration enthalpies of alkaline earth metals decreases with increase in ionic size. Alkaline earth metals are more hydrated than those of alkali metals due to small size of alkaline earth metals.
- They appear silvery and white. They are softer but harder than alkali metals.
- Some appears white but beryllium and magnesium appear greyish.
- Their melting and boiling points are higher than those of alkali metals because of their small size.
- They are strongly electropositive in nature. Electropositive character increases from beryllium to barium.
- Alkaline earth metals give different color with flame test such as calcium gives brick red color, strontium gives crimson color and barium gives apple green color.
- They have high electrical and thermal conductivities.
Fig. 3. Ionization enthalpies and atomic radii of alkaline earth metals
- Reactivity towards air and water- Beryllium and magnesium do not react with oxygen and water. They are inert towards water and oxygen as they form oxide layer on their surface. But powdered beryllium burns in air to give BeO and Be3N2. Magnesium burns in air to give MgO and Mg3N2. Calcium, strontium, and barium are easily oxidized in air to form oxides and nitrides. They also react with water to form hydroxides.
2Mg(s) + O2(g) → 2MgO(s)
2Ca(s) + O2(g) → 2CaO(s)
- Reactivity towards halogens- Like alkali metals, all alkaline earth metals reacts with halogen to form halides.
Be(s) + Cl2(g) → BeCl2(s)
Be(s) + Br2(g) → BeBr2(s)
- Reactivity towards hydrogen- Except beryllium, all alkaline earth metals reacts with hydrogen to form hydrides.
- Reactivity towards acids- The alkaline earth metals readily react with acids giving out dihydrogen.
M + 2HCl → MCl2 + H2
- Reducing nature- Alkaline earth metals are strong reducing agents. They possess large negative reduction potentials. Beryllium though has less negative reduction potential but it is still reducing in nature due to large hydration energy of beryllium ion (Be2+).
- Solutions in liquid ammonia- The alkaline earth metals dissolve in liquid ammonia to give blue black color due to the formation of ammoniated ions.
- They are the constituents of alloy formation.
- Beryllium is used for manufacturing of parts of X-ray tubes.
- Magnesium-aluminum alloys are used for air craft construction.
- A suspension of magnesium hydroxide in water is known as milk of magnesia. It is used as antacid, that is, for treating acidity.
- Magnesium carbonate is a component of toothpaste.
- Radium compounds are used in radiotherapy, such as, in the treatment of cancer.
- Calcium is an important component of bones and teeth.
- Calcium is also important during muscle contraction.
- Strontium is important component of glass wares.
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