An element with a valence shell that has only one electron is typically classified as an alkali metal. The alkali metals are found in Group 1 of the periodic table, and their valence electron configuration is characterized by having a single electron in their outermost energy level.
Here are some properties of elements with a valence shell containing only one electron:
Reactivity: Elements with a single valence electron, such as lithium (Li), sodium (Na), and potassium (K), are highly reactive. They readily lose their single valence electron to achieve a more stable configuration, typically forming a +1 cation. This reactivity is due to the relatively low ionization energy required to remove a single electron.
Metallic behavior: Elements with a single valence electron exhibit metallic behavior. They have a tendency to form metallic bonds, which involve the sharing of valence electrons among a sea of positive ions. This behavior contributes to their characteristic properties, such as good conductivity of heat and electricity.
Softness and low density: Alkali metals are generally soft and have low densities. This softness is attributed to the weak metallic bonds that can be easily disrupted. As a result, alkali metals can be cut with a knife or even shaped by hand pressure.
Low melting and boiling points: Alkali metals have relatively low melting and boiling points compared to other elements. This property is due to the weak metallic bonds and the low energy required to overcome intermolecular forces.
High reactivity with water: Alkali metals react vigorously with water, producing hydrogen gas and an alkali metal hydroxide. This reaction is exothermic and can be quite explosive in the case of more reactive alkali metals like sodium and potassium.
Flame coloration: When alkali metals are exposed to a flame, they emit characteristic colors. For example, lithium produces a red flame, sodium produces a yellow flame, and potassium produces a violet flame. These colors result from the excitation and subsequent emission of electrons in the metal atoms.
It's important to note that while these properties generally apply to elements with a single valence electron, there can be variations within the alkali metal group, and the specific properties can be influenced by factors such as atomic size, electron shielding, and nuclear charge.