Alkaline Earth Metals: Definition, Properties and Examples

Alkaline earth metals

Edited By Shivani Poonia | Updated on Jul 02, 2025 05:58 PM IST

The alkaline earth metals are a team of six chemicals within the periodic desk made up using beryllium(Be), magnesium(Mg), calcium(Ca), strontium(Sr), barium(Ba), and radium(Ra). All of these elements have various properties that are physical and chemical in nature which ensures they find use across different industries and life forms. Alkaline earth metals are shiny, silvery-white in color, and high density such as alkali metals. As they are more metallic (i.e. the bonding is stronger) their melting points and boiling points tend to be higher than those of alkali metals This is the case for their electronic configuration containing 2 electrons in s-orbitals of the highest energy which they tend to lose forming diatomic cations hence +2 oxidation state.

This Story also Contains

Alkaline Earth Metals(Physical Properties)-
Some Solved Examples
Conclusion

Alkaline earth Metals

Alkaline Earth Metals: Uses, Safety, and Some Important Points An example is beryllium dust, which is so toxic that it causes chronic lung disease and berylliosis. These barium compounds are useful but they need to be handled with care as all of them contain barium which is one of the toxic elements. Because radium is radioactive, it carries several health hazards and requires regulated management

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Alkaline Earth Metals(Physical Properties)-

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 up to 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.
Ionization energy
The alkaline earth metals have low ionization enthalpies due to the fairly large size of the atoms. Since the atomic size increases down the group, their ionization enthalpy decreases. The first ionization 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 ionization 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 ionization enthalpy value decreases.

Some Solved Examples

Q.1 Which of the following has 2s² outermost electronic configuration?

1) Mg

2) Li

3) Be

4) B

Solution:

As we learned

Electronic Configuration of beryllium -

4Be→1s22s2 or [He]2s2

Electronic configuration of Be: 1s² 2s²

Hence, the answer is the option (3).

Q 2. Which of the following has the smallest atomic size?

1) Mg

2) Be

3) Sr

4) Ca

Solution:

As we learned

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.

As we move down the group, the atomic size of elements increases, so Be has the smallest size.

Hence, the answer is the option (2).

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NCERT Chemistry Notes:

Conclusion

These observations led to the conclusion that alkaline earth metals are important both industrially and in biological systems. Many of their unique characteristics make composites vital throughout many industries and sectors, from construction to manufacturing; love them or hate them: composite materials are here to stay!!! The possibilities of these truly amazing substances are likely to become even broader as research and technology continue to evolve. Calcium and magnesium, in particular, are important for maintaining human health by supporting bone formation as well as enzymatic activities. Thus, the broad applicability and biological significance of alkaline earth metals reveal their inescapable impact on new technologies as well as life itself.

Frequently Asked Questions (FAQs)

1. What are alkaline earth metals?

Alkaline earth metals are a group 2 of the periodic table. They include beryllium, magnesium, calcium, strontium, barium, and radium.

2. Why are they called alkaline earth metals?

They are called alkaline earth metals because their oxides are basic.

3. How do alkaline earth metals react with water?

Alkaline earth metals react with water to form hydroxides and hydrogen gas. The reactivity increases from beryllium to barium.

4. Why is radium radioactive?

Radium is radioactive because its nucleus is unstable and decays over time, emitting radiation in the form of alpha particles, beta particles, and gamma rays.

5. What are the common properties of alkaline earth metals?

Alkaline earth metals are shiny, silvery-white, and somewhat reactive at standard temperature and pressure. They have two electrons in their outermost shell.

6. What are alkaline earth metals and where are they found in the periodic table?

Alkaline earth metals are a group of six elements found in Group 2 of the periodic table. They include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra). These elements are called "alkaline earth" because they form alkaline solutions when combined with water and are found in the earth's crust.

7. Why do alkaline earth metals have lower reactivity compared to alkali metals?

Alkaline earth metals have lower reactivity than alkali metals because they have two valence electrons instead of one. This makes it harder to remove electrons and form ions, resulting in a lower tendency to react. Additionally, alkaline earth metals have smaller atomic radii and higher ionization energies compared to alkali metals in the same period.

8. How does the reactivity of alkaline earth metals change as you move down the group?

The reactivity of alkaline earth metals increases as you move down the group. This is because the atomic size increases, making it easier to lose electrons. The outermost electrons are farther from the nucleus and less tightly held, resulting in lower ionization energies and higher reactivity for elements lower in the group.

9. Why do alkaline earth metals form ionic compounds with a 2+ charge?

Alkaline earth metals form ionic compounds with a 2+ charge because they have two valence electrons in their outermost shell. To achieve a stable electron configuration like that of noble gases, they tend to lose both of these electrons, resulting in a +2 oxidation state.

10. How do the melting and boiling points of alkaline earth metals compare to those of alkali metals?

Alkaline earth metals generally have higher melting and boiling points than alkali metals. This is due to the stronger metallic bonding in alkaline earth metals, which results from the presence of two valence electrons per atom instead of one. The increased number of electrons available for bonding leads to stronger interatomic forces and higher melting and boiling points.

11. What is the flame test, and how is it used to identify alkaline earth metals?

The flame test is a qualitative analysis method used to identify the presence of certain metal ions based on the characteristic color they produce when heated in a flame. For alkaline earth metals, calcium produces a brick-red flame, strontium gives a crimson red flame, and barium produces a pale green flame. This test is useful for quickly identifying these metals in unknown samples.

12. Why do alkaline earth metals form hydrides, and how do these hydrides react with water?

Alkaline earth metals form hydrides because they can react directly with hydrogen gas. These hydrides are ionic compounds where the metal has a +2 charge and the hydride ion (H-) has a -1 charge. When alkaline earth metal hydrides react with water, they produce the metal hydroxide and hydrogen gas. For example: CaH2 + 2H2O → Ca(OH)2 + 2H2

13. How does the solubility of alkaline earth metal hydroxides change down the group?

The solubility of alkaline earth metal hydroxides increases as you move down the group. This trend is due to the increasing size of the metal ions, which leads to weaker attractions between the metal cations and hydroxide anions. As a result, it becomes easier for water molecules to separate the ions and dissolve the compound. For example, Mg(OH)2 is less soluble than Ca(OH)2, which is less soluble than Ba(OH)2.

14. What is the diagonal relationship, and how does it apply to beryllium?

The diagonal relationship refers to similarities in properties between elements diagonally adjacent to each other in the periodic table. Beryllium, the first element in Group 2, shows a diagonal relationship with aluminum in Group 13. This relationship results in similar chemical properties, such as forming covalent compounds and having amphoteric oxides and hydroxides. The diagonal relationship is due to the similar charge-to-size ratios of the ions.

15. Why is beryllium considered an anomalous member of the alkaline earth metals?

Beryllium is considered an anomalous member of the alkaline earth metals because its properties often differ from the general trends observed in the group. This is due to its small size, high charge density, and high ionization energy. Beryllium tends to form covalent rather than ionic compounds, has a higher melting point than expected, and its hydroxide is amphoteric (reacts as both an acid and a base) unlike other alkaline earth metal hydroxides.

16. How do alkaline earth metals react with oxygen, and what types of compounds are formed?

Alkaline earth metals react with oxygen to form oxides. The general reaction is: 2M + O2 → 2MO, where M represents the alkaline earth metal. For example, magnesium burns in oxygen to form magnesium oxide (MgO). These oxides are typically ionic compounds with a crystalline structure. However, beryllium oxide (BeO) is an exception, as it has some covalent character due to beryllium's small size and high charge density.

17. What is the trend in the thermal stability of alkaline earth metal carbonates?

The thermal stability of alkaline earth metal carbonates increases as you move down the group. This means that carbonates of heavier alkaline earth metals decompose at higher temperatures. For example, magnesium carbonate decomposes more easily than calcium carbonate, which in turn decomposes more easily than barium carbonate. This trend is due to the increasing size of the metal ions, which leads to stronger ionic bonds and greater lattice energy in the carbonate compounds.

18. How do alkaline earth metals react with water, and how does this reactivity change down the group?

Alkaline earth metals react with water to produce metal hydroxides and hydrogen gas. The general reaction is: M + 2H2O → M(OH)2 + H2, where M is the alkaline earth metal. The reactivity increases as you move down the group. Beryllium does not react with water, magnesium reacts slowly with steam, calcium reacts with cold water, and barium reacts vigorously with cold water. This trend is due to the increasing atomic size and decreasing ionization energy down the group.

19. Why do alkaline earth metals form complexes less readily than transition metals?

Alkaline earth metals form complexes less readily than transition metals because they lack d-orbitals that can accept electron pairs from ligands. Transition metals have partially filled d-orbitals, which allow them to form strong coordinate covalent bonds with ligands. In contrast, alkaline earth metals have only s-orbitals in their valence shell, limiting their ability to form complex ions. Additionally, their larger ionic size and lower charge density make them less effective at attracting ligands.

20. How does the hardness of water relate to alkaline earth metals?

Water hardness is primarily caused by the presence of dissolved calcium and magnesium ions, which are alkaline earth metals. Hard water contains high concentrations of these ions, typically from limestone (CaCO3) or dolomite (CaMg(CO3)2) deposits. The hardness can be temporary (due to bicarbonates) or permanent (due to sulfates and chlorides). Understanding the chemistry of these alkaline earth metal ions is crucial for water treatment and softening processes.

21. What is the difference between the flame colors of strontium and calcium, and why is this important?

Strontium produces a crimson red flame, while calcium produces a brick-red flame. This difference is important because it allows for the identification and differentiation of these elements in qualitative analysis. The distinct flame colors are due to the unique electron configurations of each element, which result in different energy transitions when excited by heat. This property is used in fireworks to produce various red colors and in analytical chemistry for element identification.

22. How do alkaline earth metals compare to transition metals in terms of their ability to form colored compounds?

Alkaline earth metals generally form colorless compounds, while many transition metals form colored compounds. This difference is due to the electronic structure of these elements. Alkaline earth metals have a full outer s-orbital and no d-orbitals, which limits their ability to absorb visible light. Transition metals, on the other hand, have partially filled d-orbitals that allow for d-d electron transitions, resulting in the absorption of specific wavelengths of visible light and thus producing colored compounds.

23. Why is magnesium often used in alloys, and what properties does it impart?

Magnesium is often used in alloys because of its low density (about 2/3 that of aluminum) and high strength-to-weight ratio. When added to alloys, magnesium imparts properties such as lightness, improved strength, and increased corrosion resistance. These characteristics make magnesium alloys valuable in industries like aerospace, automotive, and electronics, where weight reduction is crucial. The ability of magnesium to form strong, lightweight alloys is related to its small atomic size and its tendency to form intermetallic compounds with other metals.

24. How does the reactivity of alkaline earth metals with nitrogen compare to their reactivity with oxygen?

Alkaline earth metals generally react less vigorously with nitrogen compared to oxygen. This is because the nitrogen molecule (N2) has a strong triple bond that requires more energy to break than the double bond in oxygen (O2). As a result, alkaline earth metals form nitrides (M3N2) less readily than oxides (MO). However, the reactivity with nitrogen increases down the group, with heavier alkaline earth metals forming nitrides more easily. For example, magnesium requires heating to react with nitrogen, while barium can react at room temperature.

25. What is the biological significance of calcium and magnesium among the alkaline earth metals?

Calcium and magnesium are the most biologically important alkaline earth metals. Calcium is crucial for bone and tooth formation, muscle contraction, nerve signaling, and blood clotting. Magnesium is essential for enzyme function, energy production, and DNA synthesis. Both elements play vital roles in maintaining proper cellular function and are involved in numerous biochemical processes. Their importance stems from their ability to form stable complexes with biological molecules and their roles in maintaining ion balance in living systems.

26. How do the atomic and ionic radii of alkaline earth metals compare to those of alkali metals in the same period?

Alkaline earth metals have smaller atomic and ionic radii compared to alkali metals in the same period. This is because alkaline earth metals have one more proton in their nucleus and one more electron in their electron shell, increasing the nuclear charge. The higher nuclear charge pulls the electrons closer to the nucleus, resulting in a smaller atomic radius. When forming ions, alkaline earth metals lose two electrons to form 2+ ions, which are smaller than the 1+ ions formed by alkali metals due to the increased effective nuclear charge acting on fewer electrons.

27. Why do alkaline earth metals have higher first ionization energies than alkali metals?

Alkaline earth metals have higher first ionization energies than alkali metals because of their smaller atomic size and higher effective nuclear charge. The valence electrons in alkaline earth metals are held more tightly to the nucleus due to the increased nuclear charge and decreased shielding effect. This makes it more difficult to remove the first electron from an alkaline earth metal atom compared to an alkali metal atom in the same period. However, the second ionization energy of alkaline earth metals is much higher than the first, as it involves removing an electron from a stable noble gas configuration.

28. How does the electronegativity of alkaline earth metals change down the group, and why?

The electronegativity of alkaline earth metals decreases as you move down the group. This trend occurs because the atomic size increases down the group, while the nuclear charge becomes more shielded by inner electron shells. As a result, the attraction between the nucleus and the valence electrons weakens, making it easier for the atom to give up electrons and harder to attract electrons. This decrease in electronegativity affects the chemical behavior of these elements, influencing their reactivity and the types of bonds they form.

29. What is the importance of calcium carbonate in nature and industry?

Calcium carbonate (CaCO3) is a versatile compound with significant importance in both nature and industry. In nature, it is the primary component of shells, pearls, and limestone formations. It plays a crucial role in the carbon cycle and ocean acidification processes. In industry, calcium carbonate is used in construction materials (cement, concrete), as a filler in paper and plastics, in antacids and dietary supplements, and in water treatment. Its abundance, low toxicity, and chemical properties make it a valuable resource in various applications, highlighting the importance of understanding alkaline earth metal chemistry.

30. How do alkaline earth metals behave in liquid ammonia, and how does this compare to alkali metals?

Alkaline earth metals, like alkali metals, dissolve in liquid ammonia to form solutions. However, there are some differences in their behavior. Alkaline earth metals form less stable solutions in liquid ammonia compared to alkali metals. When dissolved, they produce a pale blue color, which is less intense than the deep blue color produced by alkali metals. This is because alkaline earth metals form divalent ions (M2+) and release fewer free electrons into the solution. The solutions of alkaline earth metals in liquid ammonia are also less reducing than those of alkali metals due to the lower concentration of solvated electrons.

31. Why do alkaline earth metals form peroxides, and how do these differ from their normal oxides?

Alkaline earth metals can form peroxides when reacted with excess oxygen, particularly under high pressure or temperature conditions. Peroxides contain the O2^2- ion, as opposed to the O^2- ion found in normal oxides. For example, barium can form barium peroxide (BaO2) in addition to its normal oxide (BaO). Peroxides are more reactive than normal oxides and can act as oxidizing agents. The ability to form peroxides increases down the group, with heavier alkaline earth metals forming more stable peroxides. This trend is related to the increasing size of the metal ions, which can better accommodate the larger peroxide ion.

32. How does the solubility of alkaline earth metal sulfates change down the group, and why is this trend important?

The solubility of alkaline earth metal sulfates generally decreases as you move down the group. This trend is opposite to that observed for most other salts of alkaline earth metals. Beryllium sulfate is highly soluble, magnesium sulfate is soluble, calcium sulfate is slightly soluble, and barium sulfate is nearly insoluble in water. This trend is important in various applications, such as qualitative analysis in chemistry (barium sulfate's insolubility is used to test for sulfate ions) and in medicine (barium sulfate's insolubility makes it useful as a contrast agent in X-ray imaging of the digestive tract).

33. What is the difference between quicklime and slaked lime, and how are they related to calcium?

Quicklime and slaked lime are two important calcium compounds with different properties and uses. Quicklime is calcium oxide (CaO), produced by heating limestone (CaCO3) in a process called calcination: CaCO3 → CaO + CO2. Slaked lime is calcium hydroxide (Ca(OH)2), formed when quicklime reacts with water in a process called slaking: CaO + H2O → Ca(OH)2. This reaction is highly exothermic. Quicklime is used in steel production and water treatment, while slaked lime is used in mortar, plaster, and as a pH regulator. Understanding the relationship between these compounds is crucial for their proper use in industry and construction.

34. How do the reducing properties of alkaline earth metals compare to those of alkali metals?

Alkaline earth metals are generally weaker reducing agents compared to alkali metals. This is because alkaline earth metals have higher ionization energies and electronegativity values than alkali metals in the same period. As a result, alkaline earth metals have a lower tendency to lose electrons and form positive ions. For example, while sodium can reduce water at room temperature, producing hydrogen gas, magnesium only reacts with steam at high temperatures. This difference in reducing power affects their reactivity and the types of reactions they can undergo, which is important in understanding their chemical behavior and applications.

35. Why do alkaline earth metals form more covalent compounds than alkali metals?

Alkaline earth metals form more covalent compounds than alkali metals due to their higher charge density (charge-to-size ratio). The 2+ ions of alkaline earth metals have a stronger polarizing effect on surrounding anions compared to the 1+ ions of alkali metals. This increased polarization can distort the electron clouds of anions, leading to some sharing of electrons and thus more covalent character in the bonds. This effect is most pronounced with beryllium, which forms predominantly covalent compounds due to its small size and high charge density. Understanding this trend is crucial for predicting and explaining the properties of alkaline earth metal compounds.

36. How does the reactivity of alkaline earth metals with halogens compare to their reactivity with oxygen?

Alkaline earth metals generally react more vigorously with halogens than with oxygen. This is because halogens are more electronegative than oxygen and form stronger ionic bonds with the metals