A short living one,
short lifetime, fast gone.
The fifth halogenide, theoretical,
no one has seen it at all.

Astatine, „The unstable“,
a long time an empty spot on the table,
predicted but not identified,
and then as radioactive one denied.

Corson, MacKenzie and Segrè,
managed it one day,
others tried and failed before,
a cyclotron child once more.

It is part of the Neptunium decay,
in nature, too short to stay,
to use it for cancer medication,
it requires artificial creation.

High energy, low life span,
is what Astatine can,
no one will ever see it,
its radioactivity produces too much heat,