Dalton estimated atomic weights based on the mass ratios in which they combined, taking the hydrogen atom as the unit. Dalton, however, did not think that with certain elements, atoms exist in molecules – for example, pure oxygen exists in the form of O2. He also mistakenly believed that the simplest connection between two elements is always an atom of each (so he thought water was HO, not H2O). [17] This, in addition to the crudity of his equipment, was marred by errors in his results. For example, in 1803, he believed that oxygen atoms were 5.5 times heavier than hydrogen atoms because he measured 5.5 grams of oxygen to 1 gram of hydrogen in water and believed that the formula for water was HO. Using better data, he concluded in 1806 that the atomic weight of oxygen should actually be 7 instead of 5.5. And he kept that weight for the rest of his life. Others had already concluded at that time that the oxygen atom 8 relative to hydrogen must weigh 1 if we assume Dalton`s formula for the water molecule (HO), or 16 if we assume the formula of modern water (H2O). [18] One of the most important advantages of Dalton`s atomic theory is the fact that the theory does not violate several fundamental laws of chemical combination, such as the law of definite proportions, the law of multiple proportions, and the law of conservation of mass. Another important advantage of Dalton`s atomic theory is that it provided scientists with a basis for distinguishing elements and compounds.
Thomas Thomson published the first brief presentation of Dalton`s atomic theory in the third edition of his book A System of Chemistry. In 1808, Dalton published a more detailed account in the first part of A New System of Chemical Philosophy.[14] [15] However, it was not until 1811 that Dalton provided his justification for his theory of multiple proportions. [16] You`re probably thinking of the popular (non-scientific) definitions of the words „theory” and „law.” But scientists mean something quite different when they talk about theories and laws. Of course, given human nature, it is not always entirely clear what we mean by these words; The definition you get varies depending on who you ask and the context in which the words are used 😉 The distinction between „law” and „theory” is central in physics. With the same bold font: „The field of physics is the observable world.” If we can`t find a way to test it, then „it`s not physics.” Until then, it`s just like, „a physics maybe — we don`t know yet.” And these strong claims are true „by definition.” The practice was tolerant and permissive. IMO, it`s important to focus on good vision. Through his own work and that of his students Bohr and Henry Moseley, Rutherford knew that the positive charge of an atom could always be likened to that of an entire number of hydrogen nuclei. This, coupled with the atomic mass of many elements, which roughly corresponds to a whole number of hydrogen atoms – which were considered the lightest particles at the time – led him to conclude that hydrogen nuclei are singular particles and a fundamental component of all atomic nuclei. He called such particles proton. Further experiments by Rutherford revealed that the nuclear mass of most atoms exceeded that of the protons it possessed; He hypothesized that this excess mass consisted of previously unnecessarily unknown charged particles, tentatively called „neutrons”. For example – a law like this in Aristotle`s time: a block of water ice is converted into liquid when heated above 0° (suppose they have a reasonable finger as a thermometer). A guy went to the top of a high mountain and confirmed that the ice was becoming liquid at a temperature below 0º.
He will repeat the conditions of the law and advance a theory: The God of fire does not love the God of ice; Ditto to the god who reigns in the high mountains. Now we have developed explanations (theories) based on the concept of energy. In the past, the will and power of the gods was „energy.” With regard to the same law of „melting ice”, we have believed in different explanatory theories over time. Quantum theory revolutionized physics in the early 20th century. Max Planck and Albert Einstein postulated that light energy is emitted or absorbed in discrete quantities called quanta (singular, quanta). While the atoms of an element all had the same size and mass, different elements had atoms of different sizes and masses. In 1803, in a lecture to the Manchester Literary and Philosophical Society on the solubility of various gases such as carbon dioxide and nitrogen in water, Dalton referred to a list of relative atomic weights for a number of substances. Dalton did not specify how he obtained the relative weights, but he first hypothesized that the variation in solubility was due to differences in the mass and complexity of the gas particles — an idea he abandoned when the paper was finally published in 1805. [12] Over the years, several historians have attributed the development of Dalton`s atomic theory to his study of gas solubility, but a recent study of his laboratory notebook entries concludes that he developed the chemical atomic theory in 1803 to reconcile the analytical data of Cavendish and Lavoisier on the composition of nitric acid, and not to explain the solubility of gases in water. [13] Since it states that atoms cannot be created or destroyed, Dalton`s theory suggests that the net mass of species involved in a chemical reaction is conserved. This postulate therefore explains the law of conservation of mass.
Theory: A coherent set of tested general statements that are generally considered correct and can be used as principles of explanation and prediction for a class of phenomena Simply put, while a law states that something happens, a theory explains why and how something happens.