What is Coulombic Attraction? How to Find? –Best Tips!

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Coulombic Attraction

The definition of Coulombic Attraction is the Attraction between oppositely charges particles.

So basically, we are looking at and discovering what forces are holding the atom together, and one of those forces is what we call a columbic attraction. The positive force of the proton or the positive charge of the proton and the negative charge of the electron are attracting each other, and you know pulling towards each other with a force that’s going to keep that atom together.

For example, there are positively charged protons in the nucleus of an atom. Those protons have Attraction towards the negatively charged electrons, which are placed around the nucleus. This is also a Coulombic Attraction.

By using Coulomb’s law, we can calculate the force between the two charged particles. If two particles have opposite charges, the force will be Attraction. But if both particles have the same charges, the force will be repulsion.

coulombic attraction and repulsion

From this article, we are going to describe widely,

  • Factors that affect coulombic Attraction.
  • Coulombic equation.
  • Coulombic Attraction trend through the Period table

Factors that affect Coulombic Attraction

Two factors are going to kind of drive this Coulombic Attraction.

  1. Distance between charged particles.
  2. The number of protons in the nucleus.

So, let’s discuss the above factors one by one.

Distance Between Charged Particles

That means The distance between the protons in the nucleus and the electrons on the outside. In particular, we take a look at the electrons that are farthest out from the nucleus because those are going to be either held tightly or held not so tightly depending on the distance.

The Farther away they are, the Weaker the Attractive Force

Coulombic Attraction

Firstly, have a look at the above figure. According to that, here we can see that the farther out the electrons are right, the weaker the attractive force. So the smaller sized arrow is meaning that it’s a weaker force.

The Nearer they are, the Stronger the Attractive Force

As in the above figure,  the closer they are so you know if we take a look at lithium up here. That distance between the protons in the nucleus and the electron on the outside isn’t very far. So we can see that the arrow is very thick, meaning it’s a strong, attractive force.

So, let’s have a look at the second factor that affects the Coulomb’s Attraction.

The Number of Protons in the Nucleus

Now we are going to consider the number of protons in the nucleus or the magnitude of the charge.  The more charge means stronger the attractive force.

Distance and Attractive Force
Distance and Attractive Force

We can sort this out simply by following the following figure. We can see that, If you had just one proton, the force is 2.3 × 10-8 N. However, if we had four protons, we can see that the force went up quite a bit.

So the more magnitude or, the more particles you have inside your nucleus then, the stronger the attractive force can be.

Coulombic equation

So, we can put the following mathematical relationships, the two factors that the Coulumbic Attraction depends on.

We saw that the first factor was the distance. Further, you are away; the higher the distance, the less the force. What that means is that the,

  • The force of Coulomb Attraction is inversely proportional to the distance between the particles.
  • The force of Coulomb Attraction is directly proportional to the magnitude of charge. (Number of particles)

So, the mathematically derived Coulomb’s equation is,

F = kq1q2 / r2

  • F = Attraction Force (N)
  • k = Coulomb’s constant. This value is depending on the type of medium. It is approximately 9.0 x 109 N m2 C-2.
  • q1 = Charge of the First particle (c)
  • q2 = Charge of the second particle (c)
  • r = Distance between two particles (m)
Coulomb equation

Factors that determine the strength of coulombic Attraction?

Like we discussed the factors that affect Coulomb’s Attraction, two factors determine the strength of the Attraction. They are,

  1. The Size of the atom
  2. The Charge of the atom

1. Size of the atom

When the size of the atom is getting bigger and bigger, the distance between the nucleus and valence electrons will increase. As a result of that, the ability to pull electrons to the nucleus will decrease. That means the coulombic attraction force will decrease as well.

We can prove this by using the coulombic equation as well.

F = kq1q2 / r2

If we consider k, q1, q2 are constant values. Then,

F α 1 / r2

r α 1 / √F

As we can see, r value is inverse proportional to the Coulombic force. When the r value increases, the F value will decrease. r means the distance between the nucleus and the valence electron. So when the size of the atom increase, the r value is also increasing. As a result of that, the F value decreases.

2. Charge of the atom

With the change of the charge of an atom, the coulombic force will also change according to that. Atom gets a positive charge by releasing electrons and a negative charge by gaining electrons.

The Coulombic Attraction force increases with the increase of Positive charge, and The Coulombic Attraction force decreases with the increase of Negative charge.

We can derive the above statement by using the equation.

F = kq1q2 / r2

If we consider k, r,q1 are constant values. Then,

F α q2

As we can see, r value is inverse proportional to the Coulombic force. When the q2 value increases, the F value also will increase. q2 means the charge of the atom. So when the Charge of the atom increase, the q2 value is also increasing. As a result of that, the F value Increases.

Coulombic Attraction Periodic Trend

So, let’s discuss how Coulombic Attraction differs from element to element across the periodic table. Because of this attraction force of the positively charged nucleus, the electrons are placed around it. This attraction force of the nucleus depends on the type of the atom. It differs from element to element. The amount of protons in the nucleus of an atom directly affects its attraction force. Let’s see how the Coulomb attraction trend changes through periods and groups.

  1. Coulombic Attraction Increases along the period.
  2. Coulombic Attraction Decreases along with the group.
coulomb attraction periodic trend

Let’s discuss each of them one by one.

1. Coulombic Attraction Increases along the period

The coulombic Attraction increases along with the period because of the size of the atom. The size of the atom decreases with the electronegativity of an atom. So along the period, the electronegativity of elements will increase. As a result of that, the size of the atoms should decrease.

r α 1 / √F

According to the coulomb equation, the distance between two charged particles is inverse proportional to the attraction force. So, when the size of the atom decreases, the r value is also decreased. Because of that, The coulombic Attraction increases along the period.

2. Coulombic Attraction Decreases along with the group

The coulombic Attraction decreases along with the group because of the size of the atom. The size of the atom increases with the atomic number of an atom. So along with the group, the atomic number of elements will increase. As a result of that, the size of the atoms should increase.

r α 1 / √F

According to the coulomb equation, the distance between two charged particles is inverse proportional to the attraction force. So, when the size of the atom increases, the r value is also increased. Because of that, The coulombic Attraction decreases along the period.

Coulomb Attraction Summary

Coulombic Attraction is the Attraction between oppositely charges particles.

Distance between charged particles and The number of protons in the nucleus are the two factors that affect the Attraction—coulombic Attraction Increases along with the period and Decreases along with the group.

So, we hope you gained good knowledge about Coulombic Attraction and how it differs from element to element as well.

Also Read – Avogadro’s Hypothesis

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