Is the smallest particle that is characteristic of a

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Unformatted text preview: ) Hydrogen (H2) Wine Pizza Atom is the smallest particle that is characteristic of a given element. They are the building block of matter. If we split the atom any further, we lose the identity of that atom and end up with subatomic particles that are the same regardless from which atom they come from (e.g. protons from hydrogen are the same as those from helium). Inquisitive Chemist 1.5: Are atoms real? In 1981, Gerd Binnig and Heinrich Rohrer at the IBM Corporation discovered the scanning tunneling microscope (STM) that has achieved magnifications of up to 10 million, allowing chemists to look directly at individual atoms. They won a Nobel Prize in Physics in 1986. An extensive STM image gallery (including the initial atom manipulations by the IBM team) can be found at http://www.almaden.ibm.com/vis/stm/gallery.html. • Each element is made of the same kind of atoms. It is a collection of one kind (type) of atoms and cannot be decomposed into simpler substance. The symbols on the periodic table (Figure 1.3) represent elements. There are 117 known elements. Only group 8 elements exist as single atoms; all other elements exist in more complex forms. Hydrogen and helium (the two lightest elements) are the most abundant elements in the universe accounting for about 97% of the universe. The human body and earth’s crust have oxygen as the most abundant element. Only group 8 elements exist as single atoms. All other elements are found in more complex forms. The existence of an element in more than one form is called allotropy. Allotropes are made from the same atoms, but they are simply in a different form (arrangement) and thereby have different properties. This could be the result of differences in molecular structures (“normal” oxygen gas: O2 and ozone: O3), or the result of differences in packing of molecules in the solid (carbon: graphite, diamond, buckyball, nanotube). All allotropes of carbon can be viewed at http://en.wikipedia.org/wiki/Allotropes_of_carbon. 14 Copyright © 2007 by Concise Books Publishing LLC. Visit us at www.concisechem.com to download other free chapters from "The Concise Guide to Chemistry." CHAPTER 1: INTRODUCTION TO CHEMISTRY Figure 1.4: Periodic Table of Elements • A compound is made of two or more different kinds of atoms. The smallest obtainable piece of a compound is called a molecule. For example, water (a compound) is made of many H2O molecules. Each of these is made of two different types of atoms: hydrogen (H) atoms and oxygen (O) atom. Since a molecule is composed of two or more different kinds of atoms, we can break them chemically down into its constituent atoms. For example, water (liquid) can be broken down chemically (by electrolysis) into hydrogen (gas) and oxygen (gas). As seen with water, compounds have very different properties from their component elements. All compounds can be represented by chemical formulas, which show the constituent elements and the number of atoms of each consti...
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