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Alkaline Earth Metals - Practice Questions & MCQ

Edited By admin | Updated on Sep 18, 2023 18:35 AM | #JEE Main

Quick Facts

  • Alkaline Earth Metals(Chemical Properties) - 1, Alkaline Earth Metals(Chemical Properties) - 2 are considered the most difficult concepts.

  • Alkaline Earth Metals(Physical Properties) - 1 are considered the most asked concepts.

  • 145 Questions around this concept.

Solve by difficulty

Given below are two statements :

Statement I : Lithium and Magnesium do not form superoxide

Statement II : The ionic radius of Li^{+}is larger than ionic radius of Mg^{2+}

In the light of the above statements, choose the most appropriate answer from the options given below:

A metal M  readily forms its sulphate MSO_{4}  which is water­-soluble. It forms its oxide MO  which becomes inert on heating. It forms an insoluble hydroxide M(OH)_{2}  which is soluble in NaOH  solution. Then M is 

The number and type of bonds between two carbon atoms in calcium carbide are

The ion having the highest hydration enthalpy among the given alkaline earth metal ions is:

The element playing significant role in neuromuscular function and interneuronal transmission is :

Concepts Covered - 0

Alkaline Earth Metals(Physical Properties) - 1
  • Electronic configuration
    These elements have two electrons in the s-orbital of the valence shell. Their general electronic configuration may be represented as [noble gas]ns2. Like alkali metals, the compounds of these elements are also predominantly ionic.
  • Atomic and Ionic Radii
    The atomic and ionic radii of the alkaline earth metals are smaller than those of the corresponding alkali metals in the same periods. This is due to the increased nuclear charge in these elements. Within the group, the atomic and ionic radii increase with the increase in atomic number.
  • Density
    These metals are denser than alkali metals in the same period because these can be packed more tightly due to their greater nuclear charge and smaller size. The density decreases slightly upto calcium and then increases up to radium.
  • Melting and Boiling points
    The melting and boiling points of these elements are higher than the corresponding alkali metals. This is due to the presence of two electrons in the valence shell and thus, strongly bonded in the solid-state. However, melting and boiling points do not show any regular trend because atoms adopt different crystal structures.
  • Ionisation energy
    The alkaline earth metals have low ionization enthalpies due to fairly large size of the atoms. Since the atomic size increases down the group, their ionization enthalpy decreases. The first ionisation enthalpies of the alkaline earth metals are higher than those of the corresponding Group 1 metals.  This is due to their small size as compared to the corresponding alkali metals. It is interesting to note that the second ionisation enthalpies of the alkaline earth metals are smaller than those of the corresponding alkali metals.
  • Electropositive or metallic character
    The electropositive character of these elements increases down the group as the ionisation enthalpy value decreases.
Alkaline Earth Metals(Physical Properties) - 2
  • Oxidation states
    The lattice energy increases as the charge on the ion increases. The increase in the lattice energy on account of the second electron from ns2 is much more than the energy required to remove it. Thus, the stability of the +2 oxidation state is due to high lattice energy. Another reason, responsible for the +2 oxidation state is the hydration energy which is high for M2+ ions. 
  • Flame colouration
    In the case of Ca, Sr, Ba and Ra, the electrons can be excited by the supply of energy to higher energy levels. When the excited electrons return to the original level, the energy is released in the form of light. In beryllium and magnesium, the electrons are tightly held and hence excitation is rather difficult, thus do not show flame colouration.
Alkaline Earth Metals(Chemical Properties) - 1
  • Reaction with water
    Calcium, strontium, barium and radium decompose cold water readily with evolution of hydrogen
    \mathrm{M\: +\: 2H_{2}O\: \rightarrow \: M(OH)_{2}\: +\: H_{2}}
    Magnesium decomposes boiling water but beryllium does not react with water, even when red hot, its protective oxide film survives even at high temperature as its oxidation potential is lower than the other members.
  • Reactivity towards atmosphere
    Except beryllium, these metals are easily tarnished in air as a layer of oxide is formed on their surface. The effect of atmosphere increases as the atomic number increases. Barium in powdered form bursts into flame on exposure to air.
    \mathrm{M\: +\: air\: \rightarrow \: MO\: +\: M_{3}N_{2}}
  • Reactivity towards acids
    Like alkali metals, the alkaline earth metals freely react with acids and displace hydrogen.
    \mathrm{M\: +\: H_{2}SO_{4} \rightarrow \: MSO_{4}\: +\: H_{2}}
Alkaline Earth Metals(Chemical Properties) - 2
  • Reaction with carbon
    With the exception of Be, other metals when heated with carbon in an electric furnace or when their oxides are heated with carbon form carbides of the type MC2. These carbides are called acetylides as on hydrolysis they evolve acetylene
    \mathrm{MC_{2}\: +\: 2H_{2}O\: \rightarrow \: M(OH)_{2}\: +\: C_{2}H_{2}}
  • Solutions of metals in liquid ammonia
    Like alkali metals, alkaline earth metals also dissolve in liquid ammonia to form coloured solutions. Dilute solutioins are bright blue in colour due to solvated electrons. These solutions decompose very slowly forming amides and evolving hydrogen. When the solution is evaporated, hexammoniate, M(NH3)6, is formed. These slowly decompose to givve amides.
    \mathrm{M(NH_{3})_{6}\: \rightarrow \: M(NH_{2})_{2}\: +\: 4NH_{3}\: +\: H_{2}}
  • Reaction with hydrogen
    Except beryllium, all combine with hydrogen directly to form hydrides of the type MH2 when heated with hydrogen.
    \mathrm{M\: +\: H_{2}\: \rightarrow \: MH_{2}}
    BeH2 and MgH2 are covalent in nature while other hydrides are ioninc in nature. Calcium, strontium and barium hydrides liberate hydrogen at anode on electrolysis in the fused state. Ionic hydrides are violently decomposed by water eveolving hydrogen. CaH2 is used for the production of hydrogen. The hydrides are food reducting agents.
    \mathrm{CaH_{2}\: +\: 2H_{2}O\: \rightarrow \: Ca(OH_{2})\: +\: 2H_{2}}

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