One of Crookes’ most important contributions to atomic theory was his work with cathode rays. It provided evidence for the existence of elements that were previously unknown and showed that elements could be discovered through their spectral lines. Thallium’s discovery had significant implications for atomic theory. He named it after the Greek word “thallos,” meaning “a green shoot or twig.” This line did not correspond to any known element at the time.Ĭrookes investigated further and eventually isolated thallium from a sample of sulfuric acid that had been treated with selenium.

He observed a bright green line in the spectrum produced by a sample of selenium that had been exposed to sunlight. In 1861, Crookes discovered the element thallium while conducting experiments on selenium. It was during this time that he developed his skills in precision engineering and gained a deeper understanding of scientific principles. At the age of 16, he began working as an apprentice for a local firm that manufactured optical instruments. The Early YearsĬrookes showed an early interest in science and technology. Despite his humble beginnings, Crookes went on to become one of the most influential scientists of his time. Born in London on June 17, 1832, he was the eldest son of a successful tailor. Sir William Crookes was a renowned British physicist and chemist who made significant contributions to the field of atomic theory.

William crookes atomic theory