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Why is hydrogen placed in Group 1 even though it is a nonmetal?

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Periodic table of the elements with color-coded categories and labeled element groups, showing atomic numbers, symbols, and basic information for each chemical element. — periodic table Modern version of the periodic table of the elements. To learn an element's name, atomic number, electron configuration, atomic weight, and more, select one from the table.

Hydrogen is placed in Group 1 of the periodic table primarily because it possesses a single electron in its outermost valence shell. In the periodic table, the chemical properties of an element are largely determined by the number of electrons in this outermost shell, and because hydrogen, lithium, and sodium all share this single-electron configuration, they are grouped together in the same column.12

However, it is important to clarify that hydrogen is not an alkali metal; it is a gas at room temperature and does not share the metallic properties of the other elements in Group 1. Hydrogen is considered a unique, individualistic element that does not fit perfectly into any group. While it can exhibit properties similar to Group 1 elements by forming compounds with a +1 oxidation number, it can also behave similarly to Group 17 halogens by forming compounds with a -1 oxidation number, such as in lithium hydride.23