Alkali Metals

• Alkali metals are located in Group 1 of the Periodic Table and include Lithium (Li), Sodium (Na), Potassium (K), Rubidium (Rb), Cesium (Cs), and Francium (Fr).
• These metals are known for being soft and for having relatively low melting points.
• Alkali metals are highly reactive, especially with water, and their reactivity increases as you move down the Group. For example, Lithium reacts mildly with water, Sodium reacts vigorously, while Potassium reacts violently.
• Upon reacting with water, alkali metals form a metal hydroxide and hydrogen gas. This reaction can be generalised with the equation 2M(s) + 2H2O(l) -> 2MOH(aq) + H2(g), where M represents an alkali metal.
• All alkali metals have one electron in their outermost energy level. This results in similar chemical behaviour across the group.
• When an alkali metal loses this single outer electron during a reaction, it forms a positive ion (a cation).
• These elements have low electronegativity values and large atomic radii so they are great conductors of electricity and heat.
• Due to their high reactivity, alkali metals are usually stored in oil to prevent contact with air and moisture.
• Alkali metals form ionic compounds with non-metals, such as halogens. The compounds formed are white and crystalline, commonly soluble in water.
• In flame tests, different alkali metals burn with different distinctive colours. Lithium burns with a crimson flame, Sodium with a yellow flame and Potassium with a lilac flame. This can be useful in identifying the presence of these metals.
• Alkali metals, when introduced in a flame can also absorb energy and move to a higher energy level. When they fall back to their original energy level, they emit light of a specific wavelength.
• Be careful: due to their high reactivity, handling of alkali metals should be done with utmost caution. They can cause explosions or even combust when in contact with air.