Alkali Metals vs. Alkaline Earth Metals

What's the Difference?

Alkali metals and alkaline earth metals are both groups of elements found in the periodic table. However, they have distinct differences. Alkali metals, such as lithium, sodium, and potassium, are highly reactive and have a single valence electron. They are soft, silvery-white metals that are easily cut with a knife. Alkaline earth metals, on the other hand, are less reactive than alkali metals but still more reactive than most other elements. Examples of alkaline earth metals include magnesium, calcium, and barium. They have two valence electrons and are harder and denser than alkali metals. Additionally, alkaline earth metals have higher melting and boiling points compared to alkali metals.


AttributeAlkali MetalsAlkaline Earth Metals
Atomic Number1-73-12
Valence Electrons12
Electron Configuration[noble gas] ns1[noble gas] ns2
Physical State at Room TemperatureSolidSolid
Density (g/cm³)0.53-0.971.55-5.5
Melting Point (°C)28.5-39.1650-1541
Boiling Point (°C)671-11571090-2870
ReactivityHighly reactiveReactive
Ionization Energy (kJ/mol)375-590590-900
Common CompoundsNaCl, KCl, LiFCaCO3, MgSO4, BaCl2

Further Detail


Alkali metals and alkaline earth metals are two groups of elements found in the periodic table. While they share some similarities, they also have distinct differences in their properties and behaviors. In this article, we will explore and compare the attributes of alkali metals and alkaline earth metals, shedding light on their atomic structure, physical properties, chemical reactivity, and biological significance.

Atomic Structure

Both alkali metals and alkaline earth metals belong to the s-block of the periodic table, meaning their valence electrons are located in the s-orbital. Alkali metals, including lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr), have one valence electron, while alkaline earth metals, such as beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra), have two valence electrons. This difference in valence electrons contributes to their contrasting properties.

Physical Properties

Alkali metals are known for their low density, low melting points, and low boiling points. They are soft and can be easily cut with a knife. These metals have a silvery appearance when freshly cut, but quickly tarnish in air due to their high reactivity. Alkaline earth metals, on the other hand, are denser, have higher melting points, and are harder compared to alkali metals. They also exhibit a silvery-white appearance, but are less reactive and tarnish at a slower rate than alkali metals.

Chemical Reactivity

Alkali metals are the most reactive group of elements in the periodic table. Due to their low ionization energies, they readily lose their valence electron to form a +1 cation. This high reactivity makes them highly reactive with water, oxygen, and halogens. For example, when alkali metals react with water, they produce hydrogen gas and an alkaline solution. Alkaline earth metals, although less reactive than alkali metals, still possess a strong tendency to lose their two valence electrons, forming a +2 cation. They also react with water, but at a slower rate compared to alkali metals.

Biological Significance

Both alkali metals and alkaline earth metals play crucial roles in biological systems. Alkali metals, particularly sodium and potassium, are essential for maintaining proper nerve function and regulating fluid balance in the body. These elements are involved in nerve impulse transmission and muscle contraction. Alkaline earth metals, such as calcium and magnesium, are vital for bone health and muscle function. Calcium is a key component of bones and teeth, while magnesium is involved in various enzymatic reactions and plays a role in DNA synthesis.


Alkali metals find numerous applications in various industries. For instance, sodium is widely used in the production of chemicals, soaps, and detergents. Potassium is essential for fertilizers, while lithium is used in batteries and pharmaceuticals. Alkaline earth metals also have significant applications. Calcium is used in the production of cement, while magnesium is employed in the manufacturing of lightweight alloys and as a component in fireworks. Barium compounds are utilized in medical imaging, and strontium is employed in the production of pyrotechnics.


Alkali metals and alkaline earth metals share similarities in their atomic structure, physical appearance, and biological significance. However, their contrasting properties in terms of reactivity, density, and melting points set them apart. Alkali metals are highly reactive, have low densities, and low melting points, while alkaline earth metals are less reactive, denser, and have higher melting points. Understanding the attributes of these two groups of elements is crucial for comprehending their behavior and applications in various fields.

Comparisons may contain inaccurate information about people, places, or facts. Please report any issues.