In this lesson, you’ll learn what strong force is, how it holds an atom together, and how it is balanced by electromagnetic repulsion.
A short quiz will follow.
Have you ever wondered how the atom is held together? When people sit in chemistry class, a lot of the time they don’t notice an inherent issue in the structure of the atom. The nucleus of the atom contains neutrally charged neutrons and positively charged protons. Opposite charges attract and like charges repel, just like with the north and south poles of a magnet. So how is it that the positive protons stick together? Shouldn’t they be running away from each other as fast as they can?Well, they actually should. And the reason they don’t is because of the strong nuclear force.
What Is the Strong Force?
In physics, there are four fundamental forces: gravity, the electromagnetic force, the weak force, and the strong force.
The strong force is, unsurprisingly, strong. The strong force is the force that holds the nucleus of the atom together, even though other forces want to pull it apart. The electrostatic repulsion, part of the electromagnetic force, between the positive protons in the nucleus is very powerful. So the strong force has to be strong to overcome this. The strong force only works in the nucleus of the atom. This is because it has a very short range. Even the electrons are too far away to be affected by the strong nuclear force.
How Strong Force Works
There’s another thing you might not have noticed in chemistry class. As you go down the periodic table into larger and larger atoms, the number of neutrons starts to balloon rapidly. From atoms like Helium, which has two protons and two neutrons, the same number of each, you quickly get to the point where there are far more neutrons than protons, an effect that only gets more crazy the further down you go. There is a reason for this, and again, it’s because of the strong force.The way the strong force works is that the force increases with every nucleon, with every extra particle in the nucleus of the atom. As you go down the periodic table, you add an extra proton with each element, and those protons with their positive charges only increase the desire for the protons to repel each other and fly apart. The strong force increases, but not as much as the electrostatic repulsion.
But when you add a neutrally charged neutron, you increase the strong force just as much, without adding any extra repulsion. So as you go down the periodic table, you need more and more neutrons to make the strong force strong enough to hold the thing together. For example, platinum has 78 protons, but 117 neutrons.
And Rutherfordiam has 104 protons, but a full 157 neutrons!
In physics, there are four fundamental forces: gravity, the electromagnetic force, the weak force, and the strong force. The strong force is indeed very strong, because it holds the nucleus of the atom together, even though electrostatic repulsion between positive electrons wants to pull it apart. The strong force only works in the nucleus of the atom. This is because it has a very short range.The strong force is the reason that there are so many neutrons in the heavier elements.
Protons are positively charged, and adding them makes the nucleus want to repel and fly apart. But the strong force gets stronger not only when you add protons, but also when you add neutrons. Adding neutrons increases the strong force without increasing the repulsive force. So heavier elements need increasing numbers of neutrons to hold themselves together and stay stable.