Final answer:
Cesium has the lowest electronegativity (EN) among the main group elements with a value of 0.79, indicating its low tendency to attract electrons compared to other elements.
Step-by-step explanation:
The element that would have the lowest electronegativity (EN) is cesium, with an EN value of 0.79. Electronegativity is the tendency of an atom to attract a bonding pair of electrons. In the periodic table, electronegativity generally increases as you move from left to right across a period and from bottom to top within a group. Since cesium is located at the bottom left of the periodic table, it has the lowest EN compared to the other nonradioactive main group elements.
When predicting the behavior of elements in reactions, EN values can be useful. For example, fluorine, with the highest EN value of 4.0, will have a much higher tendency to gain electrons compared to cesium. This difference in EN can lead to the formation of ionic bonds when elements like cesium and fluorine combine.