Chemistry

Atoms and Molecules


Atomic Radii of Some Common Elements


Element Atomic radius
(Radius of atom)		Element Atomic radius
(Radius of atom)
1.Hydrogen 0.037 nm
2.Carbon 0.077 nm
3.Nitrogen 0.074 nm
4.Oxygen 0.073 nm
5.Chlorine 0.099 nm
6.Sulphur 0.104 nm		7.Sodium 0.191 nm
8.Magnesium 0.160 nm
9.Calcium 0.197 nm
10.Iron 0.126 nm
11.Copper 0.128 nm
12.Gold 0.144 nm

Atoms are so small that we cannot see them even under the most powerful optical microscope. Electron microscope (which uses electrons for its working) can produce extremely magnified images of tiny objects.The most advanced type of electron microscope is the Scanning Tunnelling Microscope (STM). Scanning tunnelling microscope can produce computer-generated images (pictures) of the surface of elements which show the individual atoms.The atoms show up as blurred spheres (see Figure 12).Thus,the scanning tunnelling microscope enables us to see atoms,though indirectly.

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Notes
Atoms and Molecules - Notes
1. Drawbacks of Dalton’s Atomic Theory
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2. Monovalent Cations (Cations Having a Valency of 1+)
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3. Dalton’s Symbols of Elements
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4. Divalent Cations (Cations Having a Valency of 2+)
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5. Trivalent Cations (Cations Having a Valency of 3+)
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6. Formulae of Some Molecular Compounds
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7. An Important Discussion
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8. Molecular Formulae of Some Common Elements
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9. an example, let us give the significance of symbol C
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10. Chemical Formulae
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11. As an example, let us give the significance of the formula H2O
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12. 2. A Negatively Charged Ion is Known as Anion
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13. Molecules
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14. Molecular Mass
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15. Molecules of Compounds
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16. Explanation of the Law of Conservation of Mass
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17. Some Ionic Compounds
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18. Atoms, Molecules and Ions
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19. Atoms
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20. Formula Mass
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21. Mole of Molecules
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22. Formulae of Elements
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23. 1. A Positively Charged Ion is Known as Cation
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24. Simple Ions and Compound Ions (Polyatomic Ions)
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25. 1. Molecules of Elements
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26. Symbols of Elements
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27. Gram Atomic Mass And Gram Molecular Mass
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28. John Dalton
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29. Mole of Atoms
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30. Formulae of Compounds
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31. Ions
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32. Explanation of the Law of Constant Proportions
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33. Dalton's Atomic Theory
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34. Significance of the Formula of a Substance
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35. Some Common Ions
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36. Molecular Masses of Some Common Elements
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37. Ionic Compounds
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38. Laws Of Chemical Combination
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39. Calculation of Molecular Mass
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40. Formula Unit of Ionic Compounds
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41. Divalent Anions (Anions Having a Valency of 2-)
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42. Atoms And Molecules
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43. How Do Atoms Exist
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44. Writing Of Formulae Of Ionic Compounds
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45. Problems Based On Moles Of Molecules
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46. Experiment to Verify Law of Conservation of Mass
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47. Gram Molecular Mass
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48. Gram Atomic Mass
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49. Laws Of Conservation of Mass
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50. Atomic Radii of Some Common Elements
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