Chemistry / Unit 5 Chem 0865 short lesson, about 20 seconds
Electron Configuration and Periodic Table Blocks
Captions available
The idea
The periodic table's s, p, d, and f blocks group elements whose highest-energy electron, added last by Aufbau, occupies that subshell type.
In practice
Aluminum sits in the p block because its last-added electron occupies a 3p orbital, matching [Ne]3s²3p¹.
Where people slip
An element's block is set by which subshell its Aufbau-added electron enters, not by which subshells appear anywhere in its full configuration.
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