- The s-block elements are found on the left side of the periodic table and include Group 1 (alkali metals) and Group 2 (alkaline earth metals), along with hydrogen and helium.
- These elements derive their name from the fact that their outermost electrons occupy the s-orbital of their valence shell, with general configurations of either ns¹ (for alkali metals) or ns² (for alkaline earth metals).
- Since the s-orbital can accommodate only two electrons, the s-block contains two groups and a total of 14 elements. These elements share common features such as high reactivity, low ionization energies, and a strong tendency to form ionic compounds.
- The alkali metals of Group 1 (lithium, sodium, potassium, rubidium, cesium, and francium) are soft, highly reactive metals with a single valence electron (ns¹). This electron is easily lost, making alkali metals excellent reducing agents and ensuring they always form stable +1 cations. They react vigorously with water to produce hydroxides and hydrogen gas, with reactivity increasing down the group. Alkali metals also show trends such as low melting points, decreasing ionization energy, and increasing atomic radius down the group. Their compounds, like NaCl and KOH, are essential in everyday life and industries.
- The alkaline earth metals of Group 2 (beryllium, magnesium, calcium, strontium, barium, and radium) contain two valence electrons (ns²). They are less reactive than alkali metals but still readily form +2 cations and ionic compounds. Their oxides and hydroxides are strongly basic, giving the group its name. Calcium plays a vital role in biological processes like bone formation, while magnesium is central to photosynthesis in plants. Industrially, compounds of alkaline earth metals are used in cement, steel, fireworks, and medicine.
- In addition to these, hydrogen and helium are sometimes included in the s-block. Hydrogen, with its ns¹ configuration, resembles alkali metals in terms of electron structure, though it is a nonmetal with unique chemical behavior, forming covalent and ionic compounds. Helium, with a configuration of 1s², belongs to the noble gases (Group 18) because of its chemical inertness, but it is technically part of the s-block as its valence electrons occupy the s-orbital.
- The general properties of s-block elements include low electronegativity, low ionization energy, and a strong metallic character (except for hydrogen and helium). They readily form ionic compounds with nonmetals, such as halides and oxides. Their chemical reactivity increases down the group due to weaker attraction between the nucleus and outermost electron. They are also characterized by the formation of colorless salts, strong reducing ability, and the tendency to form stable oxides and hydroxides that are basic in nature.
- In summary, the s-block elements are fundamental to both chemical reactivity and practical applications. They include some of the most reactive metals in the periodic table, and their compounds are indispensable in industries, agriculture, medicine, and biological systems. Whether in the form of sodium chloride as table salt, calcium in bones, magnesium in chlorophyll, or hydrogen as the fuel of stars, the s-block elements play a crucial role in both nature and human society.
