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 title: 1
 description: 
 published: true
-date: 2026-02-11T15:28:10.742Z
+date: 2026-02-11T15:31:01.086Z
 tags: 
 editor: ckeditor
 dateCreated: 2026-02-11T14:58:54.870Z
@@ -205,40 +205,58 @@ dateCreated: 2026-02-11T14:58:54.870Z
 <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>
+<p><span style="font-family:Arial, Helvetica, sans-serif;">1s &lt; 2s &lt; 2p &lt; 3s &lt; 3p &lt; 4s &lt; 3d</span><br>&nbsp;</p>
+<p><span style="font-family:Arial, Helvetica, sans-serif;">Imagine drawing a line from right to left.</span></p>
+<p><span style="font-family:Arial, Helvetica, sans-serif;">You should be able to find out that 4s subshell has a lower energy than 3d subshell this way.</span><br>&nbsp;</p>
 <figure class="table">
   <table>
     <tbody>
+      <tr>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>n</strong></span></td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>1</strong></span></td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
+        <td><span style="font-family:Arial, Helvetica, sans-serif;">&nbsp;</span></td>
+      </tr>
       <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 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>&nbsp;</td>
       </tr>
       <tr>
-        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">1</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>1</strong></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 style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>2</strong></span></td>
         <td>&nbsp;</td>
-        <td style="text-align:center;width:60px;">&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>3</strong></span></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>
+        <td>&nbsp;</td>
       </tr>
       <tr>
         <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
-        <td>&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>
         <td>&nbsp;</td>
         <td>&nbsp;</td>
@@ -246,55 +264,59 @@ dateCreated: 2026-02-11T14:58:54.870Z
         <td>&nbsp;</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;"><strong>2</strong></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><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;"><strong>4</strong></span></td>
         <td>&nbsp;</td>
-        <td style="text-align:center;">&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>5</strong></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 style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <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>&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 style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>3</strong></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>
+        <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;"><strong>6</strong></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;"><strong>7</strong></span></td>
       </tr>
       <tr>
         <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></td>
         <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <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>
       </tr>
       <tr>
-        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">4</span></td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>4</strong></span></td>
         <td>&nbsp;</td>
         <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4s</span></td>
         <td>&nbsp;</td>
@@ -304,21 +326,23 @@ dateCreated: 2026-02-11T14:58:54.870Z
         <td>&nbsp;</td>
         <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">4f</span></td>
         <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>8</strong></span></td>
       </tr>
       <tr>
         <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></td>
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+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></td>
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+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
-        <td>&nbsp;</td>
-        <td>&nbsp;</td>
-        <td>&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 style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5</span></td>
+        <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;"><strong>5</strong></span></td>
         <td>&nbsp;</td>
         <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5s</span></td>
         <td>&nbsp;</td>
@@ -328,6 +352,20 @@ dateCreated: 2026-02-11T14:58:54.870Z
         <td>&nbsp;</td>
         <td style="text-align:center;"><span style="font-family:Arial, Helvetica, sans-serif;">5f</span></td>
         <td>&nbsp;</td>
+        <td>&nbsp;</td>
+      </tr>
+      <tr>
+        <td>&nbsp;</td>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
+        <td style="text-align:center;width:60px;"><span style="font-family:Arial, Helvetica, sans-serif;">⁄&nbsp;</span></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>
+        <td>&nbsp;</td>
+        <td>&nbsp;</td>
       </tr>
     </tbody>
   </table>