Dichotomous keys consist of a series of statements with two choices in each step that will lead users to the correct identification. So I believe your answer would be A.
Given:
Be - Beryllium - 9,3227
C - Carbon - 11,2603
O - Oxygen - 13,6181
Ne - Neon - 21,5645
B - Boron - 8,298
Li - Lithium - 5,3917
F - Fluorine - 17,4228
N - Nitrogen - 14,5341
Arranged from highest ionization energy to lowest ionization energy.
Ne ; F ; N ; O ; C ; Be ; B ; Li
Answer:the CO2 molecule has an excess of electron
18. the blank should be "
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19. the question seems to be answered.
20. 
