. "Timeline of chemical element discoveries" . "first identified" . "few elements known since antiquity" . . . "Timeline of chemical element discoveries" . "first made" . . "timeline of chemical element discoveries" . "Discovery" . . . "identified" . "first intentionally synthesized" . "Timeline of chemical elements discoveries" . "discovers" . . . "have been observed" . "last" . . "discovery and synthesis of further new elements" . . . . "every few years" . . . . "discovery of the chemical elements" . "Discovery of the chemical elements" . . . "discovery of the element" .