Henry Moseley was a British physicist born in 1887, known for his work in atomic structure and the periodic table. He developed the concept of atomic number, which is the number of protons in an atom's nucleus. This idea helped to clarify the organization of the periodic table, leading to a more accurate arrangement of elements based on their properties. Moseley's research significantly impacted the field of chemistry and physics, as it provided a better understanding of how elements are related. Tragically, he died at a young age in 1915 during World War I, but his contributions continue to influence science today.