Why is hydrogen located where it is in the periodic table?
Because Hydrogen is in the same group (I) as the alkali metals
(Li, Na, K, etc.) without being a metal!
Hydrogen and periodic table
Hydrogen (H) is separated as it has only 1 electron and so
exhibits some unique behavior.
Most elements lose or gain electrons to reach a noble gas
configuration. Most they only do one or the other (but not both
usually). For instance fluorine (F) will always gain 1 electron to
have the electronic configuration of neon (Ne), while lithium (Li)
will always lose one electron to have the configuration of helium
Hydrogen is unique in that it can both gain one electron to have
the configuration of He, or it can lose one electron and just be a
lone proton with no electrons. A half-filled shell (in this case
the 1s orbital) is very unstable. It is better to have no electrons
or two electrons. Hydrogen can behave either like an alkali metal
and be H+ (having lost 1 electron) or can act more like a halogen
and be H- (having gained 1 electron).