Alkali metals

Definition

Alkali metals are a group of elements found in Group 1 of the periodic table, characterized by their high reactivity and tendency to lose one electron to form positive ions. These metals include lithium, sodium, potassium, rubidium, cesium, and francium, and they exhibit similar physical and chemical properties due to their single valence electron, which contributes to their placement in the periodic table.

5 Must Know Facts For Your Next Test

1. Alkali metals are soft and can be cut easily with a knife, revealing a shiny metallic luster that tarnishes quickly when exposed to air.
2. They have low melting and boiling points compared to most other metals, and these points decrease as you move down the group from lithium to francium.
3. When alkali metals react with water, they produce hydrogen gas and a corresponding alkaline hydroxide, resulting in vigorous reactions that can be explosive for heavier members.
4. The reactivity of alkali metals increases down the group; for example, francium is much more reactive than lithium.
5. Due to their high reactivity, alkali metals are not found free in nature but are always combined with other elements in compounds.

Review Questions

• Compare the properties of alkali metals with those of alkaline earth metals regarding their reactivity and electron configuration.
  • Alkali metals are generally more reactive than alkaline earth metals because they have only one valence electron, which they can easily lose to form positive ions. In contrast, alkaline earth metals have two valence electrons and require more energy to remove an electron. This difference in electron configuration leads to distinct chemical behaviors; alkali metals readily react with water and halogens, while alkaline earth metals show moderate reactivity.
• Explain how the trends in ionization energy affect the reactivity of alkali metals as you move down the group in the periodic table.
  • As you move down the group of alkali metals, ionization energy decreases due to increased atomic size and the shielding effect from inner electrons. This lower ionization energy means it is easier for these elements to lose their outermost electron, resulting in increased reactivity. Therefore, francium, being at the bottom of the group with the lowest ionization energy, is the most reactive alkali metal.
• Evaluate the implications of alkali metal reactivity on safety measures required for their storage and handling in laboratory settings.
  • Given their extreme reactivity, especially with water and air, alkali metals must be stored under oil or inert gases to prevent accidental reactions. This necessitates strict safety protocols in laboratories that handle these elements. Additionally, any experiments involving alkali metals require careful planning and protective equipment to mitigate risks such as explosions or fires. Proper training for lab personnel is essential to ensure safe practices when working with these highly reactive materials.

Related terms

alkaline earth metals: The group of elements in Group 2 of the periodic table, known for having two valence electrons and being less reactive than alkali metals.

ionization energy: The energy required to remove an electron from an atom or ion; alkali metals have low ionization energies compared to other elements, making them highly reactive.

reactivity series: A list of metals arranged in order of decreasing reactivity; alkali metals are at the top of this series due to their extreme reactivity.