Why is noble gas configuration useful?
Noble gas electron configurations are easier to write because they are shorter than full electron configurations.
To understand the chemistry of an element, it's most important to know about the electrons in the highest energy levels.
For example, the element magnesium has valence electrons (the two electrons in its highest energy level). This fact means that magnesium will form ionic compounds by donating two electrons. The magnesium ion has a +2 charge in ionic compounds (examples include MgO and
Lead has four valence electrons and its chemistry is based on this fact. Many lead compounds result from lead atoms donating 4 electrons to form +4 ions (
The Noble gas shortcut electron configuration is a way of summarizing the information about the electrons of an atom which shows only the electrons most relevant for understanding the chemistry of the element.
Here is a video which discusses how to write the Noble gas shortcut electron configuration for magnesium and lead.
Hope this helps!