41. Coordination Compound: Definition And Much More From Answers.com A chemical compound formed by joining independent molecules or ions In somecomplex ions, such as sulfate, SO42, the atoms are so tightly bound http://www.answers.com/topic/complex-chemistry

showHide_TellMeAbout2('false'); Business Entertainment Games Health ... More... On this page: Dictionary Encyclopedia WordNet Wikipedia Mentioned In Or search: - The Web - Images - News - Blogs - Shopping coordination compound Dictionary coordination compound n. A chemical compound formed by joining independent molecules or ions usually to a central metallic atom by coordinate bonds. Also called coordination complex Encyclopedia complex ion, charged molecular aggregate (see ion ), consisting of a metallic atom or ion to which is attached one or more electron-donating molecules. In some complex ions, such as sulfate, SO , the atoms are so tightly bound together that they act as a single unit. Many complex ions, however, such as tetrammine zinc (II), Zn(NH , are only loosely aggregated and tend to dissociate in a water solution until an equilibrium is established between the complex ion and its components (see chemical equilibrium ). Such complex ions, or coordinated complexes as they are also called, generally consist of a positively charged central metal atom or ion, like the zinc in tetramine zinc, surrounded by electron-donating, or basic, groups called ligands ; in the tetrammine zinc complex, the NH

42. Crystal: Definition And Much More From Answers.com crys·tal ( kris t?l ) n. A homogenous solid formed by a repeating, threedimensionalpattern of atoms, ions, or molecules and having fixed. http://www.answers.com/topic/crystal

showHide_TellMeAbout2('false'); Business Entertainment Games Health ... More... On this page: Dictionary Technology Encyclopedia Science Medical Electronics WordNet Wikipedia Translations Mentioned In Or search: - The Web - Images - News - Blogs - Shopping crystal Dictionary crys·tal krĭs təl n. A homogenous solid formed by a repeating, three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts. The unit cell of such a pattern. A mineral, especially a transparent form of quartz, having a crystalline structure, often characterized by external planar faces. A natural or synthetic crystalline material having piezoelectric or semiconducting properties. An electronic device, such as an oscillator or detector, using such a material. A high-quality, clear, colorless glass. An object, especially a vessel or ornament, made of such glass. Such objects considered as a group. A clear glass or plastic protective cover for the face of a watch or clock. Slang. A stimulant drug, usually methamphetamine, in its powdered form. adj.

43. CHEMICAL BASIS OF LIFE When atoms gain or lose electrons, they become ions. 5. Two oppositelycharged ions Two or more atoms or molecules can be joined during synthesis. http://www.sirinet.net/~jgjohnso/essentialschap2.html

BACK TO BIOLOGY II HOME PAGE ESSENTIALS OF HUMAN ANATOMY AND PHYSIOLOGY Chapter 2 - Chemical Basis of Life 2.1 Introduction (p. 32) A. Chemistry deals with the composition of substances and how they change. B. A knowledge of chemistry is necessary for the understanding of physiology. C. Body functions depend on chemical changes within cells. 2.2 Structure of Matter (p. 32) A. Elements and Atoms; (p. 32; Table 2.1) 1. All matter is composed of elements, 92 of which occur naturally. 2. Living organisms require about 20 elements, of which oxygen, carbon, hydrogen, and nitrogen are most abundant. 3. Elements are composed of atoms; atoms of different elements vary in size and in how they interact. B. Atomic Structure (p. 32; Fig. 2.1; Table 2.2) 1. An atom consists of a nucleus containing protons and neutrons, with electrons in orbit around the nucleus. 2. Protons, with a positive charge, are about equal in size to neutrons, which have no charge.

44. Atoms, Ions, Molecules And Functions I atoms, ions, molecules and Functions I. MOD 2. 1 Representation of Ethanol withVMD. In this exercise you will learn how to use the programm VMD (Visual http://lcbcpc21.epfl.ch/aimf/exercice2/exercices2.htm

Atoms, Ions, Molecules and Functions I MOD 2 1 Representation of Ethanol with VMD In this exercise you will learn how to use the programm VMD (Visual Molecular Dynamics http://www.ks.uiuc.edu/Research/vmd/), a tool to visualize the 3-dimensional structure of molecules. Go to the web page http://lcbcpc21.epfl.ch/aimf/ and download the file ethanol.pdb . This file contains the cartesian coordinates of the ethanol molecule in the pdb (Protein Data Bank) format. Open the file with a text editor and try to understand its structure. Explain briefly. Visualization of the ethanol molecule Start the programm pdb and load the file ethanol.pdb A ethanol molecule will appear on the screen. Rotation of the molecule: click on the molecule, then type ’r’. Now you can rotate the molecule with the left mouse button. Translation : proceed in the same way like for rotation but type 't' Zoom : analogous but type ’s’ Change the graphical representation of the molecule: In the smaller window ’VMD Main’ Measuring the molecule: Measuring bond lengths: Choose the drawing method 'lines'. Click on the molecule and type '2'. Now you can measure the distance between 2 atoms by clicking on the atoms from which you want to know the distances (click really on the center of both atoms).

45. Documents For An Access Point atoms, ions and molecules New results in spectral line astroph, 005086, 1991,Book, 0. 4, BH Bransden, Physics of atoms and molecules, 004627, 1983, Book http://libibm.iucaa.ernet.in/slim/wslxRSLT.php?A1=16183

46. Shapes Of Molecules And Ions Containing Single Bonds Two species (atoms, molecules or ions) are isoelectronic if they have exactlythe same number and arrangement of electrons (including the distinction http://www.chemguide.co.uk/atoms/bonding/shapes.html

SHAPES OF MOLECULES AND IONS This page explains how to work out the shapes of molecules and ions containing only single bonds. If you are interested in the shapes of molecules and ions containing double bonds, you will find a link at the bottom of the page. The electron pair repulsion theory The shape of a molecule or ion is governed by the arrangement of the electron pairs around the central atom. All you need to do is to work out how many electron pairs there are at the bonding level, and then arrange them to produce the minimum amount of repulsion between them. You have to include both bonding pairs and lone pairs. How to work out the number of electron pairs You can do this by drawing dots-and-crosses pictures, or by working out the structures of the atoms using electrons-in-boxes and worrying about promotion, hybridisation and so on. But this is all very tedious! You can get exactly the same information in a much quicker and easier way for the examples you will meet at A'level. Warning: This method won't work without some modification for many ions containing metals, and no simple method gives reliable results where the central atom is a transition metal. The method will, however, cope with all the substances that you are likely to meet in this section of the syllabus. When you deal with transition metal chemistry, you will be expected to know the shapes of some ions formed by transition metals, but not to work them out. At that point, learn the ones your syllabus wants you to know.

47. Chemistry atoms that have lost or gained electrons are called ions. The gain or loss ofelectrons Because water is polar, it bonds to ions and polar molecules. http://faculty.clintoncc.suny.edu/faculty/Michael.Gregory/files/Bio 101/Bio 101

The Biology Web (Home) General Biology 1 General Biology 2 Human Biology Chapter 4 - Chemistry Matter Matter occupies space and has weight. It can exist as a solid, liquid, or gas. It may be possible to break some kinds of matter down into other kinds of matter with different properties. For example, water (H O) can be broken down into hydrogen and oxygen. Hydrogen and oxygen in the above example cannot be broken down any further because they are elements Elements Elements cannot be broken down into substances with different properties. For example, water (H O) is not an element because it can be broken down into hydrogen (H) and oxygen (O). Substances that are composed of two or more elements are called compounds . For example, water is a compound because it is composed of hydrogen and oxygen. The smallest particle of an element is an atom Elements are substances made up of only one kind of atom. There are 92 naturally occurring elements. Matter is therefore composed of 92 different kinds of elements. The following elements make up 96% of the body weight of organisms: Oxygen, Carbon, Hydrogen, Nitrogen.

48. Chapter Eight The building units may be atoms, ions, or molecules. Copper forms atomic crystalswhich are built up on copper atoms packed together in a regular pattern http://www.3rd1000.com/chptr8.htm

8.1 MELTING AND FREEZING If the temperature of a solid is raised, according to the kinetic theory, the velocity of the particles should increase. As the temperature increases, the particles collide with each other with a greater force and, as a result, are forced farther apart. Almost all solids and liquids expand when they are heated because of this increase in velocity. If the temperature of a solid is raised sufficiently, the particles will move far enough apart to slip over one another. When such a change takes place, we say the solid has melted. The temperature at which a solid melts is called the MELTING POINT of that solid. THE NORMAL MELTING POINT IS THAT TEMPERATURE AT WHICH A SOLID BECOMES A LIQUID AT A PRESSURE OF ONE ATMOSPHERE The reverse is true of liquids. There will be some temperature ( and pressure ) at which the particles travel so slowly that they can no longer slip past one another. That temperature is called the FREEZING POINT of the liquid. THE NORMAL FREEZING POINT IS THAT TEMPERATURE AT WHICH A LIQUID BECOMES A SOLID AT 1 ATMOSPHERE OF PRESSURE . Almost all liquids have a definite freezing point, and all solids, except the amorphous forms, have a definite melting point. The freezing point of the liquid and the melting point of the solid form is the same temperature. In other words, ice melts and water freezes at the same temperature (0

49. Solids, Liquids, And Gases In the solid and liquid states, the ions or molecules are very close, It consists of molecules that contain 60 atoms of carbon linked in the form shown http://wulfenite.fandm.edu/Intro_to_Chem/solids_liquids_gases.htm

VI. Matter in Bulk B. Solids, Liquids, and Gases The three states of mattersolid, liquid, and gasdiffer primarily in two respects: a) the distance between the ions or molecules, and b) the extent to which the ions or molecules move. In the solid and liquid states, the ions or molecules are very close, whereas in the gaseous state, these particles are separated by relatively large distances. In the solid state, the ions or molecules do not translate; that is, they move around within the rigid form that constrains them. These particles do, however, vibrate about their positions. In the liquid and solid states, the particles are free to translate. Let's deal first with the nature of the substance. There four basic types of solids: a) ionic , b) molecular , c) covalent network , and d) metallic . As we know from our previous discussion of bonding, ionic compounds consist of ions. These ions are packed very efficiently to make the best use of the available space and to maximize the number of ions of opposite charge that surround a particular ion. Figure 43 shows a photo of the sodium chloride lattice (a lattice is just a regular, systematic arrangement of particles). Part (b) of this figure focuses in on a smaller part of the lattice so that we can see a sodium ion (the silver sphere in the center) surrounded by chloride ions. Molecular solids contain molecules. These molecules are also efficiently packed as shown by the model of solid carbon tetrachloride in Figure 45. The forces between molecules, called intermolecular forces, are much weaker than the electrostatic ionic forces. Consequently, the melting points of molecular solids are much lower than that of ionic solids.

50. MPS/MTP Science Links: Chemistry Links : Atoms Molecules Ions Chemistry Links atoms molecules ions. Links. atoms and ions tutorial Greattutorial on atoms and ions. Many useful links included. http://www.uwm.edu/~caberg/linksdb/Chemistry_Links/Atoms_Molecules_Ions/

Add a Resource Newsletter Advanced Search Contact Admin Search: This category All categories Top Chemistry Links : Atoms Molecules Ions Home What's New Top Rated Chemistry Links : Atoms Molecules Ions Links: Atoms and Ions tutorial - Great tutorial on atoms and ions. Many useful links included. Very nice page. pop (Added: 24-Mar-2000 Hits: 905 Rating: 10.00 Votes: 1) Rate It ChemMovies - Several multimedia clips available. Rated "very cool". Requires a FREE QuickTime plugin. (Added: 4-Apr-2000 Hits: 260 Rating: 10.00 Votes: 1) Rate It Common Monotomic Cations and Anions Game - Games to help you relate symbols of ions to thier written names. (Added: 22-Mar-2000 Hits: 292 Rating: Votes: 0) Rate It Common Names for Common Chemicals - Match the common name to the scientific name of common chemicals. (Added: 22-Mar-2000 Hits: 257 Rating: Votes: 0) Rate It Common Polyatomic Ion Games - Matching, concentration, clash card type games to relate polyatomic ion formulas and their names written out. (Added: 22-Mar-2000 Hits: 325 Rating: 7.00 Votes: 1) Rate It Common Type II Cation Game - Matching, word search, flashcards and concentration games to help in naming common type II cations.

51. Introduction To Cubic Crystal Lattice Structures The arrangement of the atoms, ions or molecules are very ordered and repeat in3dimensions. Small, 3-dimensional, repeating units called unit cells are http://www.okstate.edu/jgelder/solstate.html

Introduction to Cubic Crystal Lattice Structures The outstanding macroscopic properties of crystalline solids are rigidity, incompressibility and characteristic shape. All crystalline solids are composed of orderly arrangements of atoms, ions, or molecules. The macroscopic result of the microscopic arrangements of the atoms, ions or molecules is exhibited in the symmetrical shapes of the crystalline solids Solids are either amorphous, without form, or crystalline. In crystalline solid s the array of particles are well ordered. Crystalline solids have definite, rigid shapes with clearly defined faces. The arrangement of the atoms, ions or molecules are very ordered and repeat in 3-dimensions. Small, 3-dimensional, repeating units called unit cells are responsible for the order found in crystalline solids. The unit cell can be thought of as a box which when stacked together in 3-dimensions produces the crystal lattice. There are a limited number of unit cells which can be repeated in an orderly pattern in three dimensions. We will explore the cubic system in detail to understand the structure of most metals and a wide range of ionic compounds. In the cubic crystal system three types of arrangements are found;

52. MSN Encarta - Chemistry Crystalline materials, on the other hand, have a definite orderly array of atoms,ions, or molecules, as would a pyramid of oranges or cannonballs. http://encarta.msn.com/encyclopedia_762504460_6/Chemistry.html

MSN Home My MSN Hotmail Shopping ... Sign In Web Search: Encarta Subscriber Sign In Help Home ... Upgrade your Encarta Experience Search Encarta Upgrade your Encarta Experience Spend less time searching and more time learning. Learn more Tasks Find in this article Print Preview Related Items Chemical Analysis Chemical Reaction more... Further Reading Editors' picks for Chemistry Search for books and more related to Chemistry Encarta Search Search Encarta about Chemistry Editors' Picks Great books about your topic, Chemistry ... Click here Advertisement document.write(' Page 6 of 9 Chemistry Encyclopedia Article Multimedia 13 items Article Outline Introduction Elements and Compounds Chemical Bonds, Formulas, and Equations Physical Properties ... Branches of Chemistry C Boiling Point The boiling point of a substance is the temperature at which the liquid form of the substance changes to a gas. The boiling point is sensitive to changes in pressure , because the molecules of a substance will tend to stay in the liquid state if they are under enough pressure. A heated liquid must overcome the atmospheric pressure in order to turn into a gas (if the atmospheric pressure exceeds the vapor pressure of the boiling liquid, the liquid will be unable to turn into vapor). For this reason, water boils at lower temperatures on high mountains (where atmospheric pressure is lower) than at sea level (where atmospheric pressure is higher). The boiling point of water at a pressure of one atmosphere, or 760 mm of mercury (a standard pressure approximating sea-level pressure), is 100° on the Celsius scale and 212° on the Fahrenheit scale.

53. Laser Cooling Of Atoms, Ions, Or Molecules By Coherent Scattering Title Laser Cooling of atoms, ions, or molecules by Coherent Scattering AuthorsVuletic, Vladan; Chu, Steven Affiliation Department of Physics, http://adsabs.harvard.edu/abs/2000PhRvL..84.3787V

Smithsonian/NASA ADS Physics/Geophysics Abstract Service Find Similar Abstracts (with default settings below Electronic Refereed Journal Article (HTML) Full Refereed Journal Article (PDF/Postscript) References in the article ... Translate Abstract Title: Laser Cooling of Atoms, Ions, or Molecules by Coherent Scattering Authors: Vuletic, Vladan Chu, Steven Affiliation: Department of Physics, Stanford University, Stanford, California 94305-4060 Journal: Physical Review Letters, Volume 84, Issue 17, April 24, 2000, pp.3787-3790 ( PhRvL Homepage Publication Date: Origin: AIP; APS (c) 2000: The American Physical Society DOI: 10.1103/PhysRevLett.84.3787 Bibliographic Code: Abstract We point out a laser cooling method for atoms, molecules, or ions at low saturation and large detuning from the particles' resonances. The moving particle modifies the field inside a cavity with a time delay characteristic of the cavity linewidth, while the field acts on the particle via the light shift. The dissipative mechanism can be interpreted as Doppler cooling based on preferential scattering rather than preferential absorption. It depends on particle properties only through the coherent scattering rate, opening new possibilities for optically cooling molecules or interacting atoms. Bibtex entry for this abstract Preferred format for this abstract (see Preferences) Find Similar Abstracts: Use: Authors Title Abstract Text Return: Query Results Return

54. MAST - Math And Science Teaching Institute properties of matter including atoms, ions, elements, molecules, and density.Molecule of the Month Each month a new focus molecule is introduced to a http://mast.unco.edu/hotline/resources/chemistry_physics.php

Sunday, September 18, 2005 Home Hotline Resources : Chemistry Physics MAST MENU CENTERS CLT OTHER CHEMISTRY and PHYSICS RESOURCES Please choose the area you wish to view from the menu below: Organizations Websites and Authoritative Resources Library of MAST Chemistry and Physics Resources alphabetical listing category listing Chemistry ... Physics Do you know of a great web site that would be a good addition to this page? Please let us know by e-mailing us at: masthot@unco.edu American Association of Physics Teachers (AAPT) American Chemical Society (ACS) American Physical Society (AMS) ... Return to Subject Specific Resources Helplines and Authoritative Resources (alphabetical listing) 1001 Periodic Table Quiz Questions : this site offers free chemistry quizzes sorted by topic and grade. Armchair Chemistry : This site provides activities for middle school teachers. Awesome Library : This site provides information for chemistry and physics teachers. Center for Chemistry Education : Resources, Books, Workshops and More!! : Lots of fun and excitement for kids to do chemistry from Discovery. ChemFinder : Search to your hearts content for chemical information Educational Resources in Physics, Astronomy and Related Fields

55. CHM 230 Lab Manual Melting Point Crystalline solids are composed of atoms, ions, or molecules in a highly orderedgeometric The atoms, ions or molecules are held in their positions by http://chemlab.pc.maricopa.edu/labbooks/meltingPoint.html

56. Physics Of Atoms And Ions (Smirnov)-Springer Atoms, Molecules, Clusters And Plas Intended for advanced students of physics, chemistry, and related disciplines,this text treats the quantum theory of atoms and ions within the framework of http://www.springeronline.com/sgw/cda/frontpage/0,11855,5-10102-22-2292298-0,00.

Please enable Javascript in your browser to browse this website. Select your subdiscipline Atoms, Molecules, Clusters Biophysics Condensed Matter Geophysics Mathematical Physics Quantum Physics Home Atoms, Molecules, Clusters Select a discipline Biomedical Sciences Chemistry Computer Science Economics Education Engineering Environmental Sciences Geography Geosciences Humanities Law Life Sciences Linguistics Materials Mathematics Medicine Philosophy Popular Science Psychology Public Health Social Sciences Statistics preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900180-0,00.gif'); preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900170-0,00.gif'); preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900190-0,00.gif'); preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900200-0,00.gif'); preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900369-0,00.gif'); preloadImage('/sgw/cda/pageitems/designobject/cda_displaydesignobject/0,11978,5-0-17-900344-0,00.gif');

57. Sorting Categories Photon Interactions with atoms, ions, and molecules. 2.1 Atomic photoionizationand photodetachment processes. 2.2 Molecular photoionization http://damop2005.unl.edu/sortcategories.html

Download Sorting Categories in PDF format 1. Atomic and Molecular Structure and Properties 1.1 Spectroscopy, lifetimes, oscillator strengths 1.2 Atomic and molecular structure, including in static fields 1.3 Fundamental symmetries and precision measurements 2. Photon Interactions with Atoms, Ions, and Molecules 2.1 Atomic photoionization and photodetachment processes 2.2 Molecular photoionization, photodetachment, and photodissociation processes 2.3 Strong field (intense laser) processes 2.4 Short pulse (e.g., attosecond, femtosecond) processes 3. Atomic, Molecular, and Charged Particle Collisions 3.1 Atom-atom and atom-molecule collisions 3.2 Reactive scattering and recombination processes 3.3 Electron and positron scattering 3.4 Ion-atom and ion-ion scattering 3.5 Collisions involving clusters 3.6 Collisions involving surfaces 4. Quantum Optics, Matter Optics, and Coherent Control 4.1 Wavepacket dynamics and coherent control 4.2 Atom optics and atom interferometry 4.3 Quantum and/or nonlinear optics 4.4 Cavity QED

58. The Educational Encyclopedia, Atoms And Molecules atoms and molecules the neutron is located in the atomic nucleus (except in molecules and ions a molecule is comprised of two or more chemically bonded http://users.pandora.be/educypedia/education/chemistrymol.htm

EDUCYPEDIA The educational encyclopedia Home Electronics General Information technology ... Science Science Automotive Biology Biology-anatomy Biology-animals ... Space Social science Atlas - maps Countries Dinosaurs Environment ... Sitemap Chemistry Acids and bases Atoms and molecules Biochemistry Chemistry experiments Crystals Distillation ... Stochiometry Atomic structures Atoombouw en periodiek systeem in Dutch Atomic orbital theory Atomic orbital theory atomic orbital theory, pdf file Atomic structure Atomic structure Atomic structure Atomic structure timeline ... Atomic theory and bonding an atom consists of a small, dense nucleus containing all of its protons and neutrons, surrounded by electrons that fill the remaining volume of the atom, pdf file Atomic and molecular structure: bonding pdf file Atomic structure atomic structure, atoms, ions, protons, isotopes Atomic structure Atomic theory of matter atomic structure, doc file Atoms and molecules the neutron is located in the atomic nucleus (except in Hydrogen). The neutron has no charge, and a mass of slightly over 1 amu. Some scientists propose the neutron is made up of a proton and electron like particle. The electron is a very small particle located outside the nucleus Atoms and molecules Atoms, molecules and bonds

59. BC Education -Chemistry 11 And 12 - Atoms, Molecules, And Ions (Nomenclature) Grade 11 atoms, molecules, And ions (Nomenclature). This sub-organizer containsthe following sections Prescribed Learning Outcomes http://www.bced.gov.bc.ca/irp/chem1112/ch115.htm

Grade 11 - Atoms, Molecules, And Ions (Nomenclature) This sub-organizer contains the following sections: Prescribed Learning Outcomes Suggested Instructional Strategies Suggested Assessment Strategies Recommended Learning Resources PRESCRIBED LEARNING OUTCOMES It is expected that students will: write chemical symbols for elements and formulae for ions from appropriate charts name the ionic compound from a formula, and write the formula given a name name the covalent compound from a formula using the prefix naming system, and write the formula given a name predict the formulae of covalent compounds given the formula of another compound containing elements in the same family (families) write the names and formulae for some common acids SUGGESTED INSTRUCTIONAL STRATEGIES By learning chemical nomenclature - a systematic method of assigning names to chemical compounds - students are able to avoid memorizing thousands of names of compounds. Students are given a list of common names for compounds (e.g., wood alcohol, baking soda, aspirin) and research the chemical names and formulae. Prior to explaining a method for naming compounds, provide students with listings of chemical formulae and corresponding names and give them an opportunity to develop groupings (e.g., based on prior knowledge, analysis of commonalities). After a few minutes they should be prepared to explain and defend their groupings. Then demonstrate a method of naming ionic and binary covalent compounds.

60. Atoms & Molecules Jan 2003 Science Explorations Newsletter The compounds formed in this way are ions, rather than molecules, molecules havedifferent shapes, depending on the types of atoms bonded together. http://www.hometrainingtools.com/catalog/chemistry/articles/atoms-molecules-scie

Mon - Fri, 9am - 6pm, CST Cart My Account Wish List Help Free Catalog ... Science Kit Items More Shopping Science Kits Chemistry Kits Life Science Kits Science Fair Ideas ... Newsletter Email Updates Science Newsletter (Exclusive sales, monthly specials, new product info.) HTML Text Table of Contents Noteworthy Scientist: John Dalton (1766-1844) Science in the News: The Atom Bomb Fabulous Facts The Scientific Speaker Science Links Teaching Tip: Atoms "What is everything really made of?" Questions like this have been asked for centuries, and scientists are continually trying to find the answer. At one time scientists believed that the smallest "building block" of matter was the atom, a name that comes from the Greek word meaning "incapable of being cut." Later it was discovered that though an atom is the smallest unit that has the chemical properties of an element , even atoms are made up of smaller particles. Elements are the simplest substances found in nature and they cannot be broken down further through ordinary chemical means. At least 92 naturally occurring elements have been discovered so far. The elements are organized in a periodic table based on their different properties. To demonstrate the idea of an atom being the smallest unit of an element, take a pile of paper clips and divide it into two piles, and then divide those in half again. Continue dividing until you have one paper clip in a pile. The original pile represented matter, and you have just divided matter down to its smallest unit that still functionsone paper clip still holds loose papers together. Cut the paper clip in half. Does it still do the same job as a whole paper clip? No. In the same way, the atom is the smallest piece of an element that still functions as an element.

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