Alkaline earth metals are elements found in group 2 of the periodic table. They share similar physical and chemical traits, appearing as shiny, reactive solids. With an electron configuration of ns2, they readily form +2 cations by losing two electrons.
As known, a family of elements of the periodic table share similar properties and usually participate in similar reactions.
In this article, we’ll delve into their properties, from melting points to reactivity patterns, and discuss their importance in various fields, from industrial applications to their impact on health and the environment.
What are alkaline earth metals?
Alkaline earth metals form a group of elements found in Group 2 (IIa) of the periodic table. These six metallic elements include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).
Alkaline earth metals are silvery-white, shiny, and fairly reactive—though not as much as the alkali metals. Unlike alkali metals, they are not found free due to their high reactivity. However, they do occur naturally in various compounds and minerals.
Before the 19th century, nonmetallic and unreactive substances to fire and water were called earths. Those resembling alkalies, such as soda ash and potash, were labeled alkaline earth.
They differed from other earths like alumina and rare earths. Later, it was understood these earths were oxides, leading to the classification of their metals as alkaline-earth metals.
Alkaline earth metals are commonly found in nature, but not in their elemental form. They play vital roles in rocks, minerals, and biological systems.
Physical properties of alkaline earth metals
Melting and boiling points
These metals have remarkable melting and boiling points. For instance, magnesium (Mg) melts at around 650°C and boils at approximately 1100°C. Calcium (Ca) has a higher melting point, around 842°C, and a boiling point near 1492°C.
Density and hardness
Alkaline earth metals are relatively dense. Barium (Ba), for instance, has a density of 3.62 g/cm3. Their hardness varies, with beryllium (Be) being exceptionally hard due to its strong metallic bonds.
Metallic luster
When freshly cut, these metals exhibit a shiny, metallic luster. This property makes them visually appealing and distinguishes them from nonmetals.
Conductivity
Alkaline earth metals are good conductors of electricity. Their metallic bonding allows electrons to move freely. Magnesium, used in aerospace applications, owes its conductivity to this property.
Chemical properties of alkaline earth metals
Atomic structure and electronic configuration
Alkaline earth metals have a general electronic configuration of [noble gas] ns2. This means their outermost energy level (valence shell) contains 2 electrons.
For example, calcium (Ca) has the electronic configuration 1s22s22p63s23p64s2.
Reactivity trends
Alkaline earth metals are less reactive than alkali metals but still quite active. Their reactivity increases down the group (from beryllium to radium). Reactivity is influenced by the ease of losing those 2 valence electrons.
Oxidation states
These metals readily form +2 ions by losing their 2 valence electrons. The most stable oxidation state for alkaline earth metals is +2. For example, magnesium (Mg) forms Mg2+ ions.
Formation of oxides and hydroxides
When exposed to air or water, these metals react to form oxides and hydroxides. Magnesium oxide (MgO) is a common example:
Mg (s) + ½O2 (g) → MgO (s)
They also react with water to produce hydroxides:
Ca (s) + 2H2O (l) → Ca(OH)2 (aq)
Reactions of alkaline earth metals
Reaction with water
Alkaline earth metals react with water to form metal hydroxides and release hydrogen gas.
Example: Calcium (Ca) reacts with water
Ca (s) + 2H2O (l) → Ca(OH)2 (aq) + H2 (g)
Reaction with nitrogen (N2)
These metals react with nitrogen to form nitrides.
Example: Magnesium (Mg) reacts with nitrogen:
3Mg (s) + N2 (g) → Mg3N2 (s)
Reaction with hydrogen (H2)
These metals react with hydrogen to form hydrides.
Example: Calcium (Ca) reacts with hydrogen:
Ca (s) + H2 (g) → CaH2 (s)
Reaction with halogens (chlorine, bromine, iodine)
They react with halogens to form metal halides.
Example: Barium (Ba) reacts with chlorine:
Ba (s) + Cl2 (g) → BaCl2 (s)
Reaction with acids
These metals also react with acids to release dihydrogen gas.
Example: Strontium (Sr) reacts with hydrochloric acid:
Sr (s) + 2HCl (aq) → SrCl2 (aq) + H2 (g)
The individual alkaline earth metals
Beryllium (Be, 4)
Beryllium is the first in the series of alkaline earth metals. It is a steel-gray, lightweight but strong metal that is very brittle. Beryllium rarely exists freely in nature. It is usually found in combination with other elements in mineral forms.
It is an exception alkaline earth metal. Unlike the rest, it does not form strong alkaline hydroxides with water. Beryllium reacts with water or steam only at high temperatures and forms covalent halides.
Magnesium (Mg, 12)
This is the eighth most abundant element in the Earth’s crust. It’s a vital nutrient for plants, animals, and humans. Magnesium alloys enhance strength and lightness in aircraft and automotive parts. Magnesium sulfate (Epsom salt) soothes sore muscles and aids relaxation.
This metal also supports bone density and prevents osteoporosis. It also regulates heart rhythm and blood pressure.
Calcium (Ca, 20)
Calcium is vital in both biological systems and the fundamental structure of our planet. It is the cornerstone of our skeletal system and helps fortify bones, therefore maintaining their strength and structure.
It also regulates nerve impulses, ensuring smooth communication within our nervous system. Calcium ions are essential for muscle contraction, allowing us to move and perform daily tasks.
Calcium deficiency leads to weakened bones, increasing the risk of osteoporosis. Adequate calcium intake throughout life is vital for maintaining bone density and preventing fractures.
Calcium carbonate (CaCO3) is abundant in nature. It forms the basis of limestone, a rock found in cliffs, caves, and ancient structures.
Strontium (Sr, 38)
Strontium exists as a natural element and a radioactive element. It has four stable isotopes: 84Sr, 86Sr, 87Sr, and 88Sr, but 87Sr stands out because it is radiogenic.
It’s born from the decay of the radioactive alkali metal 87Rb (with a staggering half-life of 4.88 × 1010 years). Radioactive fallout introduced 90Sr into our environment. It’s a high-energy beta emitter.
Strontium-90 (a radioactive isotope) contaminates soil, water, and plants. It mimics calcium, infiltrating bones and preventing expulsion from the body.
Artificial 89Sr targets bone metastases while 90Sr powers nuclear-electric devices in space missions.
Barium (Ba, 56)
This alkaline earth metal boasts a range of fascinating properties and applications. With its shiny, silvery appearance, barium finds extensive use in various industries. Barium sulfate plays a crucial role in radiology. It’s used for barium enemas—a diagnostic tool to explore the human digestive tract.
Beyond medicine, barium sulfate enhances contrast in X-rays, revealing intricate details. Barium compounds find their way into drilling muds. They lubricate drill bits, making rock penetration smoother.
Barium oxide (BaO) on the other hand contributes to glass clarity and refractive properties.
Radium (Ra, 88)
Radium, an alkaline earth metal, is fascinating because it’s special and has a rich history. Marie and Pierre Curie discovered it in 1898, and it became famous for glowing and being radioactive.
People used to think it could heal, but later they found out it can be harmful because it gives off radiation. Nowadays, radium is mostly used in research and treating cancer. It’s a reminder of important scientific discoveries and inspires new ideas in science and medicine.
Applications and uses of alkaline earth metals
Alkaline earth metals have a wide range of practical applications across various industries. Here are some of them:
Aerospace and automotive industries
Magnesium alloys are lightweight and strong. They enhance fuel efficiency in aircraft and cars. These alloys are used to make parts for airplanes, cars, and even lightweight bicycles.
Biomedical implants
Magnesium-based implants promote bone healing due to their biocompatibility.
Bone health
Calcium supplements prevent osteoporosis and maintain strong bones.
Steel and glass production
Calcium is commonly used in the production of steel, as well as in the manufacturing of cement and glass. Calcium carbonate, derived from limestone, serves as a key ingredient in construction materials and paper production.
Barium in X-ray contrast media
Barium compounds, such as barium sulfate, are utilized as contrast agents in medical imaging procedures, particularly in X-ray examinations. These compounds help highlight specific areas of the body for clearer diagnostic images.
Radiotherapy
Radium was used for cancer treatment before its hazards were known. Added to that despite its radioactive nature, radium was once used in luminescent paints and clock dials. However, due to safety concerns, its applications have diminished significantly over time
Environmental impact and safety considerations
While alkaline earth metals are a group of beneficial elements, they can also negatively affect the environment and well-being.
Radioactivity of radium
Radium undergoes radioactive decay, emitting alpha, beta, and gamma radiation. Its isotopes have varying half-lives, impacting long-term exposure risks. Handling radium requires protective gear to minimize radiation exposure.
Barium toxicity
Barium toxicity affects aquatic ecosystems and soil quality.
Recycling and disposal
Proper disposal of alkaline earth metals prevents contamination. Recycling magnesium alloys, on the other hand, reduces waste and conserves resources.
FAQs
What is the comparison between alkaline earth metals and metalloids?
Alkaline earth metals (like calcium and magnesium) are shiny, hard, and good conductors of heat and electricity. They form +2 ions and are less reactive than alkali metals.
In contrast, metalloids (such as silicon and germanium) exhibit properties intermediate between metals and nonmetals, often serving as semiconductors
What is the most common oxidation state of alkaline earth metals?
+2 is the most common oxidation state of alkaline earth metals. They lose 2 electrons readily to achieve the nearest noble gas configuration.
What are the similarities between alkali metals and alkaline earth metals?
Alkali and alkaline earth metals share similarities in their high reactivity, tendency to tarnish in air, electrolytic isolation from fused chlorides, and reaction with water to form hydroxides and hydrogen gas. Despite differences, both groups exhibit similar chemical behaviors.
Conclusion
Alkaline earth metals, found in Group 2 of the periodic table, share similar traits: they are shiny, reactive solids. They easily form +2 cations by losing two electrons. Alongside playing vital roles in the body, alkaline earth metals are important elements in various industries.
As technology advances, the versatility and importance of these metals continue to be explored, which pave the way for innovative applications in the future.
Another class of metals you should learn about is the metalloids. They are unique and share properties with metals and nonmetals.
Thanks for reading.