Everything Science Grade 10

CHAPTER 4. THE ATOM 4.6

Example 4: Aufbau diagram for an ion

QUESTION

Give the electron configuration for (O^2 −) and draw an Aufbau diagram.

SOLUTION

Step 1:Give the number of electrons

Oxygen has eight electrons. The oxygen anion has gained two electrons

and so the total number of electrons is ten.

Step 2:Place two electrons in the 1 s orbital

We start by placing two electrons in the 1 s orbital: 1 s^2.

1s

Now we have eight electrons left to place in orbitals.

Step 3:Place two electrons in the 2 s orbital

We put two electrons in the 2 s orbital: 2 s^2.

1s

2s

There are now six electrons to place in orbitals.

Step 4:Place six electrons in the 2 p orbital

We place six electrons in the 2 p orbital: 2 p^6.

Step 5:Write the final answer

The electron configuration is: 1 s^22 s^22 p^6. The Aufbau diagram is:

Chemistry: Matter and Materials 85