Use the Custom Attraction feature provided on the right of the simulation to predict changes to attractive force at different points on the curve as the atomic diameter increases.
You can click the Custom Attraction radio button and set the Atom Diameter and Interaction Strength to the center using the slider bars on the right. A potential energy curve is displayed in the simulation similar to the one displayed below. The points A through E represent the position of the moving atom.
Click the Total Force radio button in the "Forces" section to observe the change in forces. The change in total force is indicated by green arrows. The arrow pointing toward the atoms shows attraction, and the arrow pointing away from the atoms show repulsion. In the simulation you can move the purple dot that represents the moving atom to each of the five points ( A to E) shown on the graph. You can do this by clicking and dragging the purple dot to the respective point on the potential energy curve.
Drag the purple point to any one of the five points ( A to E). Consider clicking on the pause button in the simulation to maintain the atom at the required point. Observe the length of the green arrow at this stage. Continue increasing the atomic diameter and observe the corresponding change in length of the arrow.
Identify how increasing the atom diameter will impact the forces experienced by the atoms at each of the five points (A to E) shown.
Drag the appropriate items to their respective bins.