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The Development of Atomic Theory

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The evolution of atomic theory is marked by significant contributions from scientists like Cannizzaro, Mendeleev, and Rutherford. Cannizzaro corrected Berzelius's atomic weight errors, leading to a better understanding of molecular composition. Mendeleev's periodic table predicted elements and reinforced atomic theory. Rutherford's experiments led to the nuclear model of the atom, changing the concept of atomic structure.

The Development of Atomic Theory: Cannizzaro's Revisions to Berzelius

The advancement of atomic theory is a story of scientific refinement and correction. Stanislao Cannizzaro played a crucial role in addressing the inaccuracies in the atomic theories of his predecessors, such as Jöns Jacob Berzelius. Berzelius incorrectly believed that gases like hydrogen and chlorine existed as single atoms, leading to errors in chemical formulas. He observed that one volume of hydrogen reacted with one volume of chlorine to produce two volumes of hydrogen chloride, which contradicted his expectations based on his atomic hypothesis. Cannizzaro argued for the concept of diatomic molecules, such as H2 and Cl2, which could dissociate into individual atoms during reactions, thus resolving the discrepancies and advancing the understanding of molecular composition.
19th century laboratory with brass scales, laboratory glassware, Bunsen burner and porcelain mortar on wooden bench under bright window.

The Philosophical Resistance to Atomic Theory and Structural Chemistry's Triumph

In the 19th century, the invisibility of atoms led to philosophical skepticism about their existence. Influenced by positivism, which advocated for the reliance on observable phenomena, some scientists dismissed atoms as mere theoretical constructs and preferred to use equivalent weights to predict chemical reactions. However, the formulation of the periodic table and the growing knowledge of molecular structure provided compelling evidence for the reality of atoms. The decline of the equivalentist perspective was hastened by the periodic table's ability to predict the properties of elements and the discovery of the internal architecture of molecules, which reinforced the atomic theory.

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00

The concept of ______ molecules, which could split into single atoms during reactions, was advocated by Cannizzaro to address the inconsistencies in earlier atomic theories.

diatomic

01

19th-century atomic skepticism

Atoms' invisibility led to doubt about their existence; positivism influenced some scientists to dismiss atoms, favoring observable phenomena.

02

Equivalent weights vs. atoms

Equivalent weights used for predicting reactions; atoms considered theoretical until molecular structure knowledge grew.

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