اختبار إلكتروني: Early Ideas About Matter

The history of atomic theory began with the ancient Greek philosopher Democritus, who first proposed that matter is made of tiny, indivisible particles called atoms. However, his ideas were not based on experimental data, and many other philosophers of the time believed matter was composed of four elements: earth, air, fire, and water. It wasn't until the early 19th century that John Dalton, a British school teacher, developed a scientific theory of the atom based on experimental observations and measurements of chemical reactions. Dalton's billiard ball model described atoms as uniform solid spheres that are indivisible and indestructible. His postulates established that atoms of a specific element are identical and that chemical reactions involve the rearrangement of these atoms. This transition from philosophical speculation to evidence-based science provided the foundation for modern chemistry.