Question

a(n) □ □ diagram uses the chemical symbol of an element surrounded by dots to represent the number of electrons in the outermost energy level.

Explanation:

In chemistry (a subfield of Natural Science), a Lewis dot diagram (also called Lewis electron - dot diagram) is defined as a diagram that uses the chemical symbol of an element surrounded by dots to represent the number of electrons in the outermost energy level (valence electrons). So the blanks should be filled with "Lewis" and "dot" (or "electron - dot").

Answer:

Lewis, dot (or Lewis, electron - dot)