Elements 89 to 103

To anyone who knows a bit about the Periodic Table, but is not an expert (and yes, I do mean me) this is an "either–or" question.

There are two groups of elements that don't fit into the basic structure of the table, but effectively all fit into one place. One is the actinides (elements 89 to 103) and the other is the lanthanoids (elements 57 to 71 – previously known as the lanthanides, and also known as the rare earths). The actinides all fit into the place occupied by actinium (element no. 89) and the lanthanoids all fit into the place occupied by lanthanum (element no. 57).

In our match, if I remember correctly, this question went to the biochemist on the other side, who knew the answer. If it had gone to our team, I wouldn't have known which one to choose – actinides or lanthanoids.

It shouldn't need to be said that you should not set either–or questions in a Quiz League format.