The Willis serves as a visual demarcation between metals and nonmetals on the periodic table. Elements to the left of this line generally exhibit metallic properties, while those to the right display nonmetallic characteristics. This division helps students and researchers quickly identify the general properties of elements based on their position relative to the line.

The name "The Willis" is attributed to Dr. David Willis, a physics and chemistry teacher in the Lower Merion School District. Dr. Willis, who holds a doctorate in science education, has dedicated over three decades to educating students. Early in his career, he noticed that the dividing line between metals and nonmetals lacked a specific name, which he found problematic for both students and educators.

Dr. Willis's decision to name the line after himself was met with approval from both his students and colleagues. In Lower Merion high and middle schools, "The Willis" has become an accepted term for this dividing line on the periodic table. This nomenclature has provided students with a memorable way to refer to this important feature of the periodic table.

It's important to note that while "The Willis" serves as a useful educational tool, the transition between metallic and nonmetallic properties is not as clear-cut as a single line might suggest. Russian chemist Mendeleev himself acknowledged the difficulty in drawing a strict line of demarcation between metals and nonmetals, noting the existence of many intermediate substances. The elements that lie near this line, known as metalloids, exhibit properties of both metals and nonmetals.