Here's why:

* Technetium is a transition metal with atomic number 43.

* All isotopes of Technetium are radioactive, meaning they decay over time. This is why it doesn't have any stable isotopes.

* Hydrogen (H), Helium (He), Lithium (Li), Beryllium (Be), Boron (B), Carbon (C), Nitrogen (N), Oxygen (O), Fluorine (F), and Neon (Ne) all have stable isotopes.

* Technetium comes before these elements on the periodic table, making it the lightest element with no stable isotopes.