Question

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

Explanation:

Longhand notation lists all electrons in an atom's orbitals. Noble - gas notation uses the symbol of the nearest noble gas with fewer electrons as a shorthand start. Potassium's $1s^{2}2s^{2}2p^{6}3s^{2}3p^{6}4s^{1}$ is longhand as it lists all orbitals. Iron's $[Ar]4s^{2}3d^{6}$ and Argon's $[Ne]3s^{2}3p^{6}$ are noble - gas notations as they start with noble - gas symbols.

Answer:

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