Step 1: Use the periodic table fact:
Technetium (Z = 43) and promethium (Z = 61) are the two lighter elements with no stable isotopes. Promethium belongs to the lanthanoids.
Step 2: Check the options:
Tm (69), Dy (66) and Eu (63) are stable. Pm (61) is not.
Step 3: Pick:
Option D.
Final Answer:
Only Pm, atomic number 61, has no stable isotope.
\[ \boxed{\text{(D) }\text{Pm}} \]