Why is hydrogen written alone on the periodic table?

Answer 1

Hydrogen is not exactly written alone on the Periodic Table. The table is organized into rows and columns, both of which represent groupings of elements for different reasons.

For example, elements in the same column (called "groups") all have the same number of free electrons, or "valence electrons". Elements in the same row have the same or similar numbers of filled electron shells.

Hydrogen is in the top row because it has only 1 electron shell and it is in the far left column because it has 1 free electron (just like all of the elements beneath it).

Helium, on the other hand, also has 1 electron shell, but is in the far right column because it has a full electron shell (no free electrons). This makes it chemically similar to all of the elements beneath it (this group is called the "noble gases" because they have no free electrons to interact with other elements).

Answer 2

Hydrogen is placed separately on the periodic table because it has unique properties that do not fit neatly into any one group. It is the simplest and most abundant element in the universe, and its characteristics are distinct from the alkali metals and halogens to which it is sometimes compared.