Everything Science Grade 10

4.6 CHAPTER 4. THE ATOM

1s

2s

There are now three electrons to place in orbitals.

Step 4:Place three electrons in the 2 p orbital

We place three electrons in the 2 p orbital: 2 p^3.

1s

2s

2p

1s

2s

2p

1s

2s

2p

Step 5:Write the final answer

The electron configuration is: 1 s^22 s^22 p^3. The Aufbau diagram is given

in the step above.

Aufbau diagrams for ions

When a neutral atom loses an electron it becomes positively charged and we call it a
cation. For example, sodium will lose one electron and become Na+or calcium will lose
two electrons and become Ca2+. In each of these cases, the outermost electron(s) will be
lost.
When a neutral atom gains an electron it becomes negatively charged and we call it an
anion. For example chlorine will gain one electron and become Cl−or oxygen will gain
two electrons and become O^2 −.
Aufbau diagrams and electron configurations can be done for cations and anions as well.
The following worked example will show you how.

84 Chemistry: Matter and Materials