Name: dalton’s laws and early atomic ideas
Uploaded: 2020-09-03T13:38:25.000Z
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North Carolina K-12 Science Standard Course of Study

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Chemistry

Matter and its Interactions

PS.Chm.1.1

The Atomic Theory of Matter

Les premiers Grecs aiment Démocrite ont d'abord avancé l'idée d'atomos, le plus petit unité indivisible de matière. Ce concept a ensuite été mis en avant sous le nom de théorie atomique par le scientifique anglais John Dalton. Le premier postulat de la théorie atomique de Dalton suggère que les éléments sont composés de minuscules particules indivisibles appelées atomes.Par exemple, l'hydrogène est constitué de deux atomes d'hydrogène liés ensemble et l'oxygène est composé de deux oxygène atomes liés ensemble. Le deuxième postulat stipule que tandis que les atomes du même élément sont identiques, ils diffèrent des atomes des autres éléments. Ainsi, tous les atomes d'hydrogène sont identiques les uns aux autres, mais diffèrent des atomes d'oxygène.Le troisième postulat stipule que les atomes d'éléments différents peuvent se combiner entre eux, dans de simples rapports de nombres entiers, pour former des composés. Par exemple, deux atomes d'hydrogène et un atome d'oxygène combinent dans un rapport de 2 à 1 pour former H2O eau. Le dernier postulat de la théorie de Dalton déclare que les réactions chimiques ne changent les atomes d'un élément en atomes d'un élément différent;au lieu de cela, les atomes existants se réorganisent pour former de nouvelles substances.Pendant la formation de l'eau, de l'hydrogène et de l'oxygène existants les atomes ne sont ni créés ni détruits, ils ne font que se réorganiser. Dalton a construit sa théorie atomique sur deux lois précédentes des réactions chimiques La loi de conservation de la masse et la loi des proportions définies. La loi de conservation des états de masse que la masse totale avant et après une réaction chimique reste constante.Ainsi, 18 grammes d'eau se décomposent en 2 grammes d'hydrogène et 16 grammes d'oxygène. La loi des proportions définies stipule qu'indépendamment de la source, dans un composé chimique donné, le rapport de masse des éléments constitutifs reste toujours fixe. Ainsi, un échantillon d'eau pure aura toujours un rapport 1 à 8 massique de l'hydrogène à l'oxygène indépendamment de la masse totale de l'eau.Dalton a ensuite proposé la loi des multiples proportions basé sur sa propre théorie. Selon cette loi, lorsque deux éléments se combinent pour former plus d'un composé, différentes masses d'un élément se combinent avec la masse fixe de l'autre élément dans un petit nombre entier. Ainsi, une masse fixe d'hydrogène, 2 grammes, se combine avec différentes masses d'oxygène, 32 ou 16 grammes, dans un petit nombre entier de 2 à 1, pour former deux composés différents le peroxyde d'hydrogène et l'eau.

la théorie atomique de la matière

La première discussion répertoriée sur la structure de base de la matière provient des philosophes de la Grèce antique. Leucippe et Démocrite soutenaient que toute la matière était composée de petites particules finies qu'ils ont appelées atomos, signifiant “ indivisible ”. Plus tard, Aristote et d'autres philosophes en sont venus à la conclusion que la matière était constituée de diverses combinaisons des quatre “ éléments ” — le feu, la terre, l'air et l'eau — et qu'elle pouvait être divisée à l'infini. Il est intéressant de noter que ces philosophes considérait les atomes et les “ éléments “ comme des concepts philosophiques, mais n’ont apparemment jamais envisagé de faire des expériences pour vérifier leurs idées.  
 
 La vision aristotélicienne de la composition de la matière exerça une emprise pendant plus de deux mille ans, jusqu'à ce que le scientifique anglais John Dalton révolutionne la chimie avec l'hypothèse que le comportement de la matière pourrait être expliqué en utilisant une théorie atomique. Publié pour la première fois en 1807, nombre des hypothèses de Dalton sur les caractéristiques microscopiques de la matière sont encore valables dans la théorie atomique moderne.  
 
 Voici les postulats de la théorie atomique de Dalton : 
 
 <ol>
 <li>La matière est composée de particules excessivement petites appelées atomes. Un atome est la plus petite unité d'un élément qui peut participer à une transformation chimique. </li>
 <li>Un élément est constitué d'un seul type d'atome, qui a une masse qui est caractéristique de l'élément et qui est la même pour tous les atomes de cet élément. Un échantillon macroscopique d'un élément contient un nombre incroyablement élevé d'atomes, qui ont tous des propriétés chimiques identiques. </li>
 <li>Les propriétés des atomes d'un élément diffèrent de celles des atomes de tous les autres éléments. </li>
 <li>Un composé est constitué d'atomes d'au moins deux éléments combinés suivant un rapport de petits nombres entiers. Dans un composé donné, le nombre d'atomes de chacun de ses éléments est toujours présent suivant le même rapport </li>
 <li>Les atomes ne sont ni créés ni détruits au cours d'une transformation chimique, mais ils sont réorganisés pour produire des substances qui sont différentes de celles présentes avant la transformation. </li>
 </ol>
 
 Dalton a utilisé trois lois de réactions chimiques comme base pour sa théorie : (1) la loi de conservation de la masse, (2) la loi des proportions définies, et (3) la loi des proportions multiples. La théorie atomique de Dalton fournit une explication microscopique pour les nombreuses propriétés macroscopiques de la matière.  
 
 La loi de conservation de la masse a été découverte par le chimiste français Antoine Lavoisier. Elle indique que les atomes ne sont ni créés ni détruits au cours d'une transformation chimique ; la masse totale de matière présente lorsque la matière change d'un type à l'autre reste constante. 
 
 Dalton connaissait aussi les expériences du chimiste français Joseph Proust, qui a démontré que tous les échantillons d'un composé pur contiennent les mêmes éléments dans la même proportion en masse. Cette déclaration est connue sous le nom de la loi de proportions définies ou la loi de composition constante. La supposition que les nombres d'atomes des éléments dans un composé donné existent toujours suivant le même rapport est cohérente avec ces observations.  
 
 Dalton a également utilisé les données de Proust, ainsi que les résultats de ses propres expériences, pour formuler une autre loi intéressante. La loi des proportions multiples stipule que lorsque deux éléments réagissent pour former plus d'un composé, une masse fixe d'un élément réagit avec les masses des autres éléments suivant un rapport de petits nombres entiers. 
 
 La théorie de Dalton a fourni un cadre qui a ensuite été élargi pour démontrer que l'atome est composé de particules subatomiques et que les atomes du même élément peuvent différer en masse, appelés isotopes. 
 
 Ce texte est adapté de <a href="https://openstax.org/books/chemistry-2e/pages/2-1-early-ideas-in-atomic-theory">Openstax, Chimie 2e, Section 2.1 : Les premières idées de la théorie atomique.</a>

La théorie atomique de la matière

La plus ancienne discussion enregistrée sur la structure de base de la matière provient des philosophes grecs de l’Antiquité. Leucippe et Démocrite ont soutenu que tout compte ...

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dalton’s laws and early atomic ideas

Dalton’s atomic theory explains matter with atoms, elements, and compounds. It also shows how chemical changes follow simple laws. This idea gave chemistry a microscopic model for what can be seen in the lab.

The earliest recorded ideas about matter came from ancient Greek philosophers. Leucippus and Democritus said all matter was made of tiny, finite particles called atomos, meaning “indivisible.” Aristotle and others later argued that matter was made from four elements: fire, earth, air, and water. They also believed matter could be divided forever, and these ideas were treated as philosophy rather than experiments.

That view lasted for more than two thousand years. Then English scientist John Dalton changed chemistry with an atomic theory of matter. He first published it in 1807. Many of his ideas still fit modern atomic theory.

Dalton’s postulates describe matter at the atomic level. Matter is made of extremely small particles called atoms. An atom is the smallest unit of an element that can take part in a chemical change. An element contains only one type of atom, and atoms of the same element have the same characteristic mass and chemical properties. Atoms of different elements have different properties. A compound is made of atoms of two or more elements joined in a small, whole-number ratio, and the ratio stays the same in a given compound. During a chemical change, atoms are not created or destroyed. They are rearranged into new substances.

Dalton built his theory using three key laws of chemistry. The law of conservation of mass says mass stays constant during a chemical change, a result linked to Antoine Lavoisier. The law of definite proportions, also called the law of constant composition, says every pure sample of a compound contains the same elements in the same mass ratio, as shown by Joseph Proust. Dalton also used the law of multiple proportions, which says that when two elements form more than one compound, fixed masses of one element combine with the other in small whole-number ratios.

Dalton’s atomic theory gives a microscopic explanation for macroscopic matter. It also helped later scientists show that atoms contain subatomic particles. Later work also showed that atoms of the same element can differ in mass, which are called isotopes.

Dalton’s Laws and Early Atomic Ideas

the atomic theory of matter

Dalton’s atomic theory explains matter with atoms, elements, and compounds. It also shows how chemical changes follow simple laws. This idea gave chemistry a microscopic model for what can be seen in the lab. The earliest recorded ideas about matter came from ancient Greek philosophers. Leucippus and Democritus said all matter was made of tiny, finite particles called atomos, meaning “indivisible.” Aristotle and others later argued that matter was made from four elements: fire, earth, air, and...

subatomic particles

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Explore Dalton’s atomic theory, the laws of conservation of mass, definite proportions, and multiple proportions, plus the early ideas that shaped modern chemistry.

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Dalton’s Laws and Early Atomic Ideas

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