![]() Compounds are formed by the joining of atoms of two or more elements.Ģ0. Atoms of different elements are different. Atoms of the same element are exactly alike. Atoms are indivisible and indestructible particles. The atomos idea was buried for approximately 2000 years.ġ8 Dalton’s Model In the early 1800s, the English Chemist John Dalton performed a number of experiments that eventually led to the acceptance of the idea of atoms.ġ9 Dalton’s Theory He deduced that all elements are composed of atoms. Their ideas held sway because of their eminence as philosophers. Aristotle and Plato favored the earth, fire, air and water approach to the nature of matter. Atoms were infinite in number, always moving and capable of joining together.ġ5 This theory was ignored and forgotten for more than 2000 years!ġ6 Why? The eminent philosophers of the time, Aristotle and Plato, had a more respected, (and ultimately wrong) theory. He named the smallest piece of matter “atomos,” meaning “not to be cut.”ġ4 Atomos To Democritus, atoms were small, hard particles that were all made of the same material but were different shapes and sizes. This idea was first proposed by Democritusġ1 The atomic model has changed throughout the centuries, starting in 400 BC, when it looked like a billiard ball →ġ2 Democritus 400 BC He asked: Could matter be divided into smaller and smaller pieces forever, or was there a limit to the number of times a piece of matter could be divided?ġ3 Atomos His theory: Matter could not be divided into smaller and smaller pieces forever, eventually the smallest possible piece would be obtained. The word “atom” comes from the Greek word “atomos” which means indivisible. Where did it all begin? This is the Greek philosopher Democritus who began the search for a description of matter more than 2400 years ago. From the early Greek concept to the modern atomic theory, scientists have built upon and modified existing models of the atom.ĩ Who are these men? In this lesson, we’ll learn about the men whose quests for knowledge about the fundamental nature of the universe helped define our views.ġ0 This idea was first proposed by Democritus Answer the questions in your Study Guide about the example of Indirect Evidence.Ĩ A model can be changed as new information is collected.Ĭan a Model be Changed? A model can be changed as new information is collected. Just like pieces being added to a puzzle, each new bit of information gives us a better understanding of atoms.Ĭlick here to visit a lab where actual scientific research on atoms is conducted. The Atomic - Molecular Theory of Matter is based upon a vast amount of indirect evidence gathered over a long period of time. (Artist drawing)Ħ Indirect Evidence Indirect Evidence is evidence gathered without being able to directly observe the object. The model above represents the most modern version of the atom. Even though we do not know what an atom looks like, scientific models must be based on evidence. It shows the parts and structure of the atom. Is this really an Atom? Many of the models that you have seen may look like the one below. Does it actually look like a young woman?ĥ The model above represents the most modern version of the atom. This is a painting of a young woman by Pablo Picasso. A model is an attempt to use familiar ideas to describe unfamiliar things in a visual way. Scientific models may not always look like the actual object. ![]() Each colored ball represents an atom of a different element. This is a model of a very complex molecule made of many different kinds of atoms. Since the atom is so small, scientists must gather Indirect Evidence to develop their models. Even with the world’s best microscopes we cannot clearly see the structure or behavior of the atom.ģ Scientific Models Scientists create models to help them to visualize complex properties, structures or behaviors. This theory is really thousands of individual theories that provide evidence for the whole theory.Ģ Matter Since the atom is too small to be seen even with the most powerful microscopes, scientists rely upon models to help us to understand the atom. These atoms can join together to form molecules. The Atomic - Molecular Theory of Matter states that all matter is composed of small, fast moving particles called atoms. Presentation on theme: "Atomic - Molecular Theory of Matter"- Presentation transcript:
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