Final answer:
When one molecule has a negative charge, it can either attract or repel other charged molecules depending on their charges. The electrostatic force determines whether the molecules will attract or repel each other.
Step-by-step explanation:
In the case of one molecule (spheres) having a negative charge, both a positively charged sphere would attract the negatively charged sphere, and a negatively charged sphere would repel the negatively charged sphere. Like charges repel each other, while opposite charges attract each other.
The reason for this attraction or repulsion is due to the electrostatic force between two charged particles. The electrostatic force is attractive between opposite charges and repulsive between like charges.
For example, when a positive object is brought near a neutral insulator, the positive object polarizes the molecules of the insulator, causing a slight shift in the electron distribution. This results in unlike charges being brought closer and like charges moving away, leading to a net attraction.