Arsenic, bismuth, and antimony were identified by alchemists during the Middle Ages, and later during the 1700 ’ s, many more elements were found.
निसर्गातील सर्व मूलद्रव्यांत अतिशय अद्‌भुत एकसूत्रीपणा असल्यामुळेच प्रत्येक मूलतत्त्वाची अॅटॉमिक संख्या निश्‍चित करणे शास्त्रज्ञांना शक्य झाले आहे. ”