Name: from atomos to the modern atom
Uploaded: 2023-06-23T15:38:43.000Z
Duration: 1 min 17 s
Channel: JoVE

K12 Standards

Pennsylvania State Academic Standards

9-12

Earth and Space Science

Space Systems

3.3.9-12.C

Atomic Structure

Chaque élément est composé de minuscules particules appelées atomes. Ces particules confèrent à chaque élément des propriétés physiques et chimiques distinctes, telles que le point d’ébullition, le point de fusion et la densité.
Tous les atomes d’un élément ont des propriétés identiques mais diffèrent de celles des autres éléments.
De telles différences sont dues aux particules subatomiques – protons, neutrons et électrons.
Les protons et les neutrons contribuent tous deux à la masse atomique, avec une unité de masse atomique chacun, tandis que les électrons ont une masse presque négligeable.
Les protons et les neutrons sont regroupés dans un noyau central. Le nombre de protons, égal au numéro atomique, détermine l’élément spécifique.
Les protons sont chargés positivement et les neutrons ne sont pas chargés, de sorte que le noyau a une charge positive nette.
Un nuage d’électrons chargés négativement est attiré par le noyau. Ce nuage est presque vide et constitue la majeure partie du volume d'un atome.
Un atome neutre contient un nombre égal de protons et d’électrons, annulant les charges positives et négatives et ne conduisant à aucune charge nette.

structure atomique

Le philosophe grec Démocrite proposa que toute chose sur Terre est constituée de petites particules appelées atomes, du mot grec "atomos" qui signifie "indivisible", d'où le terme moderne "atome". Au XIXe siècle, John Dalton proposa la théorie atomique qui est encore largement correcte aujourd'hui. Il a énoncé cinq postulats pour expliquer comment les atomes composent le monde qui nous entoure. (1) Toute la matière est composée de particules ou d'atomes infiniment petits. (2) Tous les atomes d'un élément donné sont identiques les uns aux autres et (3) sont différents des atomes de tous les autres éléments. (4) Deux éléments ou plus peuvent se combiner dans une proportion fixe pour former un composé. (5) Les atomes ne peuvent pas être créés ni détruits lors d'une réaction chimique, mais ils peuvent se réarranger pour former de nouvelles substances. Dalton avait seulement partiellement raison à propos des particules qui composent la matière. Bien que les atomes ne puissent pas être décomposés davantage par des processus chimiques ou physiques ordinaires, ils sont composés de trois plus petites particules subatomiques. Le premier indice sur la structure subatomique est venu lorsque J.J. Thomson découvrit l'électron. Les scientifiques savaient que la charge globale d'un atome était neutre, mais le modèle de "pudding aux pruneaux" de Thompson fournit de nouvelles informations concernant l'existence d'une particule chargée négativement, suggérant que les électrons étaient dispersés dans une zone chargée positivement. Plus tard, Ernest Rutherford réalisa une expérience montrant que la majeure partie de la masse d'un atome est concentrée dans le noyau, où les protons représentent la charge positive de l'atome et les petits électrons chargés négativement occupent la majeure partie de l'espace en dehors du noyau. Cela réfuta le modèle de pudding aux pruneaux de Thomson. En 1932, James Chadwick a découvert que le neutron représente la masse présente dans un atome. Selon la théorie actuellement acceptée, les protons se trouvent dans le noyau d'un atome, ont une charge positive et ont une masse d'une unité de masse atomique (UMA) chacun. Le nombre de protons correspond au numéro atomique du tableau périodique et détermine l'identité de l'élément. Les neutrons se trouvent également dans le noyau. Ils n'ont pas de charge, mais ont la même masse que les protons, contribuant à la masse atomique d'un atome. Les électrons orbitent autour du noyau en formant des nuages. Ils ont une charge négative et une masse négligeable, donc ils contribuent à la charge totale d'un atome mais pas à sa masse.

Structure atomique

Le philosophe grec Démocre a proposé que tout sur Terre est composé de minuscules particules appelées atomos, grec pour « indivisible », d’où ...

Education

Enseignement

JoVE Core

Anatomy and Physiology

Anatomie et physiologie

Unit 1

Unité 1

Fundamentals of Chemistry

Les fondamentaux de la chimie

KEY TERMS AND CONCEPTS

TERMES ET CONCEPTS CLÉS

from atomos to the modern atom

Atoms are the tiny building blocks of matter, and ideas about them go back to the Greek philosopher Democritus. He suggested that everything on Earth is made of atomos, a Greek word meaning &quot;indivisible.&quot; That idea later led to the modern word atom.

In the 19th century, John Dalton developed an atomic theory that is still largely correct today. He proposed five key ideas. All matter is made of tiny particles called atoms. Atoms of the same element are alike, and atoms of different elements are not. He also said that elements combine in fixed ratios to form compounds, and that atoms are not created or destroyed in a chemical reaction. Instead, they rearrange to make new substances.

Dalton’s model was only partly complete. Atoms cannot be broken down by ordinary chemical or physical processes, but they do contain smaller subatomic particles. The first major clue came from J. J. Thomson, who discovered the electron. At the time, scientists knew atoms were neutral overall, so Thomson’s plum pudding model suggested that negative electrons were spread through a positively charged material.

Later, Ernest Rutherford carried out an experiment that changed the atomic model. His results showed that most of an atom’s mass is packed into a central nucleus. In this model, protons provide the atom’s positive charge, and the tiny negative electrons take up most of the space outside the nucleus. This finding disproved Thomson’s plum pudding model.

In 1932, James Chadwick discovered the neutron, which explained the mass still present in the atom. In the accepted model today, protons and neutrons are in the nucleus. Protons have a positive charge and a mass of one atomic mass unit, or AMU, each. The number of protons equals the atomic number on the periodic table and defines the element. Neutrons have no charge, but they have about the same mass as protons, so they add to atomic mass. Electrons move in clouds around the nucleus. They have a negative charge and very little mass, so they affect the atom’s overall charge more than its mass.

From Atomos to the Modern Atom

what is matter?

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the periodic table and organismal elements

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atomic structure

Atoms are the tiny building blocks of matter, and ideas about them go back to the Greek philosopher Democritus. He suggested that everything on Earth is made of atomos, a Greek word meaning "indivisible." That idea later led to the modern word atom. In the 19th century, John Dalton developed an atomic theory that is still largely correct today. He proposed five key ideas. All matter is made of tiny particles called atoms. Atoms of the same element are alike, and atoms of different elements are...

chemical symbols

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isotopes and radioisotopes

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electron behavior

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From Atomos to the Modern Atom | JoVE K12

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Louisiana Student Standards for Science

High School

Chemistry

Matter And Its Interactions

HS-PS1-1

Next Generation Science Standards

Earth’s Place in the Universe

HS-ESS1-3

south-carolina-college-and-career-ready-science-standards

South Carolina College and Career Ready Science Standards

Matter and Its Interactions

C-PS1-1

C-PS1-2

C-PS1-3.

motion-and-stability-forces-and-interactions

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C-PS2-6.

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Atomic Structure of atoms

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3.3.9-12.A

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The Greek philosopher Democritus proposed that everything on Earth is made up of tiny particles called atomos, Greek for &#34;indivisible,&#34; from which ...

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3.3.9-12.D

From Atomos to the Modern Atom

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