Potassium (K): 1s22s22p63s23p64s1

The configuration lists every occupied subshell from 1s through 4s: 1s²2s²2p⁶3s²3p⁶4s¹. Longhand notation writes out all of those subshells, while noble-gas notation replaces the inner electrons with a noble-gas symbol, such as [Ar]4s¹. Therefore, this is longhand notation.

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