Final answer:
Abbreviated electron configurations use noble gases from the periodic table to represent the core electrons, simplifying the configuration of atoms with many electrons, such as lithium's [He]2s¹.
Step-by-step explanation:
To abbreviate long electron configurations, you can use the noble gases found in the last column of the periodic table. These noble gases can represent the electron configuration of all the electrons up to that noble gas. When writing such an abbreviated configuration, start with the symbol of the noble gas enclosed in brackets, followed by the configuration of the remaining electrons.
For instance, the abbreviated electron configuration for an atom of lithium (Li), which has a total of three electrons, would be represented as [He]2s¹. Here, [He] signifies the filled 1s orbital with two electrons (the electron configuration of helium), and 2s¹ represents one electron in the 2s subshell. This approach greatly simplifies the writing and reading of electron configurations for atoms with many electrons.