When is a metal not a metal?
Small clusters of naked (no ligand attached) atoms or single atoms are seen as the ultimate catalyst for achieving different types of hydrocarbon reactions (i.e. Fischer-Tropsch reactions) without catalyzing the production of undesirable materials. Recently published works aim at the production of single atoms or clusters of naked atoms, and the characterization of these is surveyed. Attempts to answer the question of how many atoms of a specific material must cluster to bring about the transition to bulk material properties are also reported. This transition of properties occurs at different numbers of atoms/cluster for physics and chemistry. (BLM)