Group 1 elements, also known as alkali metals, are the most reactive elements in the periodic table. This reactivity can be attributed to their electronic configuration and the low ionization energy associated with these elements.
The alkali metals in Group 1 have a single electron in their outermost energy level, which is relatively far from the positively charged nucleus. This outer electron is held less tightly by the nucleus compared to inner electrons, making it easier to remove or ionize. As a result, alkali metals have low ionization energies, meaning it requires less energy to remove the outermost electron and form a positively charged ion.
The low ionization energy makes alkali metals highly prone to losing their outer electron and forming a +1 cation. By losing this electron, they achieve a stable electron configuration similar to the noble gas in the previous period. This process releases a significant amount of energy and makes the alkali metals highly reactive.
Furthermore, once the outer electron is lost, the resulting cation has a large positive charge that is poorly shielded by the remaining electrons. This high charge density leads to strong electrostatic attractions with other atoms or molecules, making the alkali metals highly reactive in chemical reactions. They readily react with elements such as oxygen, water, and halogens to form compounds.
In summary, the high reactivity of alkali metals in Group 1 is primarily due to their low ionization energy, which allows them to easily lose their outermost electron and form positive ions, and the resulting high charge density of these ions, which promotes strong interactions with other atoms or molecules.