Question

which of the following electron dot notations is correct for the element argon, ar, atomic #18?

Explanation:

Argon is a noble - gas with 18 electrons and a full outer shell of 8 valence electrons. Electron - dot notation shows the valence electrons as dots around the symbol of the element. For argon, there should be 8 dots evenly distributed around the 'Ar' symbol.

Answer:

The option with 8 dots evenly placed around the 'Ar' symbol (the second and fourth options in the image seem to be the same correct one with 8 dots around 'Ar') is correct.