Coulombic Attraction is the force of attraction between particles positive and negative charges.
Opposite charges attract: positive attracts negative.
Like charges repel (positive repels positive, and negative repels negative)
Coulombic attraction force gets stronger with more charge.
Coulombic attraction gets weaker at longer distances.
Coulomb’s Law: this equation shows relationships between charge, distance, and force.
Where:
F = force between the two charges (Newtons, N)
q1 and q2 = strength of the two charges (coulombs, C)
d = distance between the charges (meters, m)
k = Coulomb’s constant = 9.0 x 109 N⋅m2C2
The force is proportional to the strength of the charges.
The force is related to the inverse square of the distance between charges.
Inverse Square example: if you multiply the distance by 5, the force would be divided by 52 or 25. This example is shown in the following table:
| Trial | distance, d | Force, F |
|---|---|---|
| #1 | 3 | 250 |
| #2 | 15 | 10 |
You can see that the distance is multiplied by 5 from Trial #1 to Trial #2. The force goes down, but it isn’t divided by 5 like it would in a regular inverse relationship. It’s inverse square, because it’s divided by 25 instead of 5.
Coulombic Attraction in Atoms:
Coulomb’s Law determines what happens to the forces within atoms when they have different amounts of charge and different distances between particles.
- Having more protons (positive charge) gives a nucleus a stronger Coulombic attraction to its own electrons and to neighboring atoms’ electrons.
- When an atom’s outermost electrons are farther away (larger distance), the Coulombic attraction gets much weaker. This happens when an atom has more occupied electron shells.
- Atoms with many shells of electrons have a shielding effect in which core electrons closer to the nucleus repel outer electrons, which tries to push them away from the nucleus.