The (2) calcium atom, because when looking at the periodic table, we see that the calcium atom is in a location where according to the periodic table, has the lower electronegativities in respect to the other three choices. We see that it also has a lower electronegativity value than the others. Electronegativity is the attraction constant for the electrons in a chemical bond. The higher the electronegativity, the higher the attraction of the electrons. Fluorine has the highest electronegativity with 4.0.