Question

identify whether longhand notation or noble - gas notation was used in each case below. potassium (k): 1s²2s²2p⁶3s²3p⁶4s¹ longhand notation noble - gas notation complete argon (ar): ne3s²3p⁶ longhand notation noble - gas notation done iron (fe): ar4s²3d⁶ longhand notation noble - gas notation complete

Explanation:

Longhand notation lists all the electron - occupied orbitals from the 1s orbital. Noble - gas notation uses the symbol of the previous noble gas in brackets and then lists the remaining electrons. For potassium (K), all orbitals are listed out, so it's longhand. For argon (Ar), [Ne] is used which is noble - gas notation. For iron (Fe), [Ar] is used, so it's noble - gas notation.

Answer:

Potassium (K): longhand notation
Argon (Ar): noble - gas notation
Iron (Fe): noble - gas notation