Answer is: creative.
To be creative means to form something new and somehow valuable.
At the begining of the 20th century, chemists were very creative and they set many new experiments to discover properties of an atom.
For example famous Rutherford's Gold Foil Experiment: he bombarded thin foil of gold with positive alpha particles (helium atom particles, consist of two protons and two neutrons).
Rutherford observed the deflection of alpha particles on the photographic film and notice that most of alpha particles passed straight through foil.
