In the periodic table hydrogen is placed in Group 1A (group 1) and helium is placed in Group 8A (group 18). The most likely reason for this is configuration, energy level and properties.
Hydrogen is located in group 1 of the periodic table, although its electronic configuration is 1s¹ and its properties do not correspond to those of the alkali metals of that group. But in its electronic configuration you can see that it has only one electron in its outermost shell (which turns out to be the only shell it has), just like any other element of group 1A /group 1, so it is located in that group.
On the other hand, although the electronic configuration of helium is 1s², this element does not appear in group 2 of the periodic table of elements, but is placed in group 18. This is because it has the energy level complete, so it has the properties of a noble gas, that is, it is inert (it does not react), and it is a colorless and odorless monatomic gas.
In summary, in the periodic table hydrogen is placed in Group 1A (group 1) and helium is placed in Group 8A (group 18). The most likely reason for this is configuration, energy level and properties.
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