john dalton atome modele

PDF	Atomic Theory ‣ No Theory is the complete story ‣ Science moves in steps ‣ Each time through the cycle we improve or replace our theories

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Daltons Atomic Theory

Dalton\'s model was that the atoms were tiny indivisible indestructible particles and that each one had a certain mass size and chemical behavior that was determined by what kind of element they were We will use that model of an atom for now but we will modify it considerably in a later lesson Top of Page E-mail instructor: Sue Eggling

How was Dalton's atomic theory different from Ancient Greek philosophy?
The ancient Greek philosophers had talked about atoms, but Dalton's theory was different in that it had the weight of careful chemical measurements behind it. It wasn't just a philosophical statement that there are atoms because there must be atoms. His atomic theory, stated that elements consisted of tiny particles called atoms.
Why did Dalton's theory have to be modified?
Part two of Dalton's theory had to be modified after mass spectrometry experiments demonstrated that atoms of the same element can have different masses because the number of neutrons can vary for different isotopes of the same element. For more on isotopes, you can watch this video on atomic number, mass number, and isotopes.
What was Dalton's model of an atom?
Dalton's model was that the atoms were tiny, indivisible, indestructible particles and that each one had a certain mass, size, and chemical behavior that was determined by what kind of element they were. We will use that model of an atom for now, but we will modify it considerably in a later lesson.
What are the tenets of atom theory?
The general tenets of this theory are as follows: All matter is composed of extremely small particles called atoms. Atoms of a given element are identical in size, mass, and other properties. Atoms of different elements differ in size, mass, and other properties. Atoms cannot be subdivided, created, or destroyed.

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. chem.ws

Scientific Method is Iterative

‣ The products of scientific method are laws and theories. ‣ These laws and theories are based on the observations available at the time they’re produced. ‣ As time moves forward we explore further. ‣ We take a more detailed look. ‣ Or consider new applications. ‣ Which brings up new questions and allows new observations. chem.ws

More Observations

‣ Last years theory — which was “good enough” for many things — may not explain all our new observations. ‣ So we offer new explanations (hypothesis) and experiment to disprove or improve them. New Hypothesis More Experiments chem.ws

Revised Laws

‣ New research produces revised theories and improved laws. chem.ws

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. ‣ ‣ ‣ ‣ chem.ws

In 1789 Antoine Lavoisier redefined the term element

to describe the twenty three pure substances that chemists had discovered but could not break down into simpler substances. ‣ This was the the first time metals other than mercury were considered elements. ‣ ‣ chem.ws

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. chem.ws

Three Laws of Stoichiometry

‣ In exploring the elements which composed all matter, chemists observed three consistent patterns. These three laws invited explanations that would result in the resurgence of atomic theory. chem.ws

John Dalton Proposed a new Atomic Theory:

‣ “Elements are composed of minute particles called atoms.” Dalton reintroduced the atom to the world. Dalton ‣ “Atoms of the same element are alike in mass and size. Atoms of different elements have different masses and sizes.” Dalton suggested that atoms come in different flavors, corresponding to the different elements. ‣ “The atoms of one el

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. chem.ws

‣ Charges can be different sizes

The properties of charged atoms were documented by Michael Faraday, who named them ions. Charged atoms move in solution, toward or away from electrically charged wires. ‣ The word “ion” is greek for wanderer. ‣ Ions that move towards a cathode (neg charged wire) are positively charged ions. chem.ws

‣ They’re called cations. CA+IONS

‣ Ions that move towards an anode (pos charged are negatively charged ions. chem.ws

‣ They’re called anions.

Atoms and ions made from those same atoms different properties. chem.ws

An Overview of Atomic Particles

We will discuss the details of these differences in the next few chapters. This slide will reappear a lot. chem.ws

‣ Properties of Cathode Rays

‣ Travel in straight lines. ‣ The ray is negatively charged. ‣ The same rays come from all of the different elements explored. ‣ The rays had mass (they can make a pin wheel spin). chem.ws

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. chem.ws

The Gold Foil Experiment

Ernest Rutherford was a student of J.J. Thomson. In an attempt to support Thomson’s plum-pudding theory of the atom Rutherford used alpha radiation to Rutherford explore the structure of the atom. chem.ws

Observations

Alpha particles mostly passed right through the gold. A small number bounced back. Some deflected as they passed through the atom.. chem.ws

Atoms are mostly empty space. Rutherford

There was something tremendously massive but small inside the atom (more massive than a helium atom). The massive part was positively charged. chem.ws

Scientific Method

‣ No Theory is the complete story ‣ Science moves in steps. ‣ Each time through the cycle, we improve or replace our theories. chem.ws

Daltons Atomic Theory 3D Animated explanation Complete Basics Chemistry Class 9th &11th

Dalton Atomic theory Some Basic Concept of Chemistry tutorial #6

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