Hydrogen is not considered a metal among the Group 1 elements because it does not exhibit typical metallic properties.
Metals in Group 1, also known as the alkali metals, include elements such as lithium, sodium, potassium, and so on. These metals have several common properties such as low electronegativity, high reactivity, low density, and the ability to form metallic bonds.
However, hydrogen is unique because it is not a metal but a nonmetal. Although it is placed above Group 1 elements in the periodic table, it is not considered a part of the group.
Hydrogen differs from the alkali metals in several ways. Firstly, it is a gas at room temperature, while the alkali metals are solid. Secondly, unlike the alkali metals, hydrogen is not highly reactive and does not readily lose an electron to form a positive ion. Instead, it tends to form covalent bonds and share electrons with other elements. Additionally, hydrogen has properties of both metals and nonmetals, making it difficult to classify into a specific category.