diff --git a/education/chemistry/1.html b/education/chemistry/1.html
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@@ -2,7 +2,7 @@
 title: 1
 description: 
 published: true
-date: 2026-02-11T15:25:43.391Z
+date: 2026-02-11T15:28:10.742Z
 tags: 
 editor: ckeditor
 dateCreated: 2026-02-11T14:58:54.870Z
@@ -202,3 +202,134 @@ dateCreated: 2026-02-11T14:58:54.870Z
     </tbody>
   </table>
 </figure>
+<p>&nbsp;</p>
+<h3><span style="font-family:Arial, Helvetica, sans-serif;">Aufbau principle</span></h3>
+<p><span style="font-family:Arial, Helvetica, sans-serif;">The lowest energy subshell or orbital will be filled first</span></p>
+<p><span style="font-family:Arial, Helvetica, sans-serif;">1s &lt; 2s &lt; 2p &lt; 3s &lt; 3p &lt; 4s &lt; 3d</span><br><br>&nbsp;</p>
+<figure class="table">
+  <table>
+    <tbody>
+      <tr>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+      </tr>
+      <tr>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">1</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">1s</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;">&nbsp;</td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;">&nbsp;</td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">2</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">2s</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">2p&nbsp;</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;">&nbsp;</td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">3</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">3s</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">3p&nbsp;</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">3d</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">4</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4s</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4p&nbsp;</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4d</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4f</span></td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5s</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5p&nbsp;</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5d</span></td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5f</span></td>
+        <td>&nbsp;</td>
+      </tr>
+    </tbody>
+  </table>
+</figure>
+<p>&nbsp;</p>