Assume that in interstellar space the distance between two electrons is about 0.56 cm. the electric force between the two electrons is 1. attractive. 2. repulsive.

The electric force is a force that is inversely proportional to the square of the distance. This can be proved by Coulomb's Law, which states:  

"The electrostatic force between two point charges and is proportional to the product of the charges and inversely proportional to the square of the distance that separates them, and has the direction of the line that joins them"  

Mathematically this law is written as:  

Where is a proportionality constant.

So, if we have two electrons, this means we have two charges with the same sign, hence the electric force between them will be repulsive.