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💏intro to chemistry review

S-block

Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025

Definition

The s-block is a group of elements in the periodic table that includes the alkali metals (group 1) and the alkaline earth metals (group 2). These elements are characterized by their high reactivity and the presence of s-orbital electrons in their valence shell.

5 Must Know Facts For Your Next Test

  1. The s-block elements are located on the far left side of the periodic table and are the most reactive of all the elements.
  2. Alkali metals have a single valence electron in their s-orbital, which is easily lost, making them highly electropositive and reactive.
  3. Alkaline earth metals have two valence electrons in their s-orbital, which are also easily lost, contributing to their high reactivity.
  4. The s-block elements have low ionization energies, meaning they readily lose their valence electrons to form positive ions, which is a key factor in their reactivity.
  5. The reactivity of the s-block elements increases down the group as the atomic radius increases and the valence electrons become more loosely held.

Review Questions

  • Explain the electronic configuration of the s-block elements and how it contributes to their high reactivity.
    • The s-block elements, which include the alkali metals and alkaline earth metals, have their valence electrons in the s-orbital. Alkali metals have a single valence electron in the s-orbital, while alkaline earth metals have two valence electrons in the s-orbital. This configuration makes the valence electrons in the s-block elements relatively loosely held, allowing them to be easily lost to form positive ions. This low ionization energy and high electropositive nature are the primary factors that contribute to the high reactivity of the s-block elements.
  • Describe the general trends in the reactivity of the s-block elements as you move down the groups.
    • The reactivity of the s-block elements increases as you move down the groups of the periodic table. This is due to the increasing atomic radius of the elements, which results in the valence electrons being held less tightly. As the atomic radius increases, the valence electrons become more loosely held, making it easier for the elements to lose their valence electrons and form positive ions. Consequently, the s-block elements become more electropositive and reactive as you move down the groups, with the alkali metals being the most reactive and the alkaline earth metals being the next most reactive.
  • Explain the importance of the s-block elements in various chemical and biological processes, and how their reactivity influences their applications.
    • The s-block elements play a crucial role in many chemical and biological processes due to their high reactivity. The alkali metals, such as sodium and potassium, are essential for maintaining the proper balance of fluids and electrolytes in the body, as well as for nerve impulse transmission. The alkaline earth metals, such as calcium and magnesium, are important for bone and tooth development, and are also involved in various enzymatic reactions. The reactivity of the s-block elements also makes them useful in various industrial applications, such as the production of glass, ceramics, and certain types of batteries. However, their high reactivity also requires special handling and storage conditions to prevent dangerous reactions with water or other substances.