1s² 2s² 2p⁶ 3s² 3p⁶ 4s² 3d¹⁰ 4p¹
Here's how to understand it:
* 1s²: The first energy level (n=1) has one subshell (s) with two electrons.
* 2s² 2p⁶: The second energy level (n=2) has two subshells, s and p, with a total of eight electrons.
* 3s² 3p⁶: The third energy level (n=3) has two subshells, s and p, with a total of eight electrons.
* 4s²: The fourth energy level (n=4) starts with the s subshell, which holds two electrons.
* 3d¹⁰: Following the filling order, the 3d subshell (which can hold up to 10 electrons) is filled next with ten electrons.
* 4p¹: Finally, the 4p subshell receives its first electron, completing the configuration for gallium.
Important Note: The filling order of electrons follows the Aufbau principle and Hund's rule, which are helpful for determining the electron configuration of elements.
