Lecture_11_Atomic_models - UNIT LECTURE 1 NOTES LECTURE 11...

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U N I T 1 L E C T U R E N O T E S LECTURE 11 Atomic Models GENERAL CHEMISTRY Fall 2009 Updated: 11/22/2011
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3.3 Dalton’s Atomic Theory John Dalton (1766 – 1844) explained observations such as the law of constant composition (a compound always has the same composition) using his theory. The predictive value of the theory led to its eventual acceptance. A. Defining the Atom 1. Atomic Theory a. All matter is made up of very tiny particles called atoms b. Atoms of the same element are chemically alike c. Individual atoms of an element may not all have the same mass. However, the atoms  of an element have a definite average mass that is characteristic of the element d. Atoms of different elements have different average masses e. Atoms are not subdivided, created, or destroyed in chemical reactions 3.5 The Structure of the Atom 1e. Students know the nucleus of the atom is much smaller than the atom yet contains most of its mass. The volume of the hydrogen nucleus is about one trillion times less than the volume of the hydrogen atom, yet the nucleus contains almost all the mass in the form of one proton. The diameter of an atom of any one of the elements is about 10,000 to 100,000 times greater than the diameter of the nucleus. The mass of the atom is densely packed in the nucleus. The electrons occupy a large region of space centered around a tiny nucleus, and so it is this region that defines the volume of the atom. If the nucleus
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Lecture_11_Atomic_models - UNIT LECTURE 1 NOTES LECTURE 11...

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