wiki/education/chemistry/1.html

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<h3><span style="font-family:Arial, Helvetica, sans-serif;">Bohr model (1913)</span></h3>
<figure class="table">
  <table>
    <tbody>
      <tr>
        <td style="text-align:center;width:200px;"><span style="font-family:Arial, Helvetica, sans-serif;">Particle</span></td>
        <td style="text-align:center;width:200px;"><span style="font-family:Arial, Helvetica, sans-serif;">Symbol</span></td>
        <td style="text-align:center;width:200px;"><span style="font-family:Arial, Helvetica, sans-serif;">Relative Charge</span></td>
        <td style="text-align:center;width:200px;"><span style="font-family:Arial, Helvetica, sans-serif;">Mass Unit</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">Electron</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">e-</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">-1</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5.4858 x 10<sup>-4</sup></span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">Proton</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">p+</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">+1</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">1.0073</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">Neutron</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">n</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">0</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">1.0073</span></td>
      </tr>
    </tbody>
  </table>
</figure>
<p>&nbsp;</p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Protons = Electrons ⇒ Atom. Neutral.</span></p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Protons ≠ Electrons ⇒ Ion. Charged.</span></p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Electrons are surrounding the nucleus, consisting of protons and neutrons.</span></p>
<p>&nbsp;</p>
<h3><span style="font-family:Arial, Helvetica, sans-serif;">Element</span></h3>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Mass number are the number of protons and neutrons in the nucleus.</span></p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Atomic number are the number of protons in nucleus.</span></p>
<p>&nbsp;</p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">For example, <sup>4</sup><sub>2</sub>He, where mass number is written on top left, and atomic number on bottom left.</span></p>
<p>&nbsp;</p>
<h3><span style="font-family:Arial, Helvetica, sans-serif;">Periodic Table</span></h3>
<p><span style="font-family:Arial, Helvetica, sans-serif;">The elements are arranged in the order of increasing atomic number, from left to right, from up to down.</span></p>
<p><span style="font-family:Arial, Helvetica, sans-serif;">Each element has a unique atomic number (or the number of proton).</span></p>
<p>&nbsp;</p>
<h3><span style="font-family:Arial, Helvetica, sans-serif;">Electronic arrangement</span></h3>
<p><span style="font-family:Arial, Helvetica, sans-serif;">The maximum number of electron that a shell can hold is 2(n)<sup>2</sup></span></p>
<p>&nbsp;</p>
<figure class="table">
  <table>
    <tbody>
      <tr>
        <td style="text-align:center;width:100px;"><span style="font-family:Arial, Helvetica, sans-serif;">n</span></td>
        <td style="text-align:center;width:100px;"><span style="font-family:Arial, Helvetica, sans-serif;">max</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">1</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">2</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">2</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">8</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">3</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">18</span></td>
      </tr>
      <tr>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4</span></td>
        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">32</span></td>
      </tr>
    </tbody>
  </table>
</figure>
<p>&nbsp;</p>