Answer:
D. 1s²2s²2p 3s²3p6
Step-by-step explanation:
The most chemically stable electron configuration is typically the one that has a full valence shell, which means that the outermost electron shell is completely filled with electrons. In this case, the electron configuration with a full valence shell is 1s²2s²2p 3s²3p6. This configuration is often called the "noble gas" configuration, because it is similar to the electron configuration of a noble gas, such as neon or argon, which are extremely stable and unreactive.