Why Does an Atom Have No Charge When It Has Charged Particles in It?

The Electric Field

Electric charges create an electric field. An electric field causes other electric charges to accelerate. In other words, you can tell if an object creates an electric field if you see that it makes other charges move. If an object creates an electric field, the object is charged.

The laws that govern the behavior of the electric field are important for human civilization. Disregarding the fact that the operation of our own bodies depends upon the electric field, the operation of our civilization is dependent upon an understanding of the rules governing this field. For situations involving the electric field of a charged body, the rule is simple. The electric field present at a surface is dependent upon the amount of charge enclosed by that surface.

The nucleus of an atom is a tight ball that contains a positive charge. The positive charge is contained in a certain number of protons, each with a charge of +1. A cloud of electrons surrounds the nucleus. The number of electrons is the same as the number of protons. Each of those electrons has a charge of -1. Now imagine a sphere surrounding the atom. The electric field at the surface of the sphere is dependent upon the charge enclosed by that surface. So what charge is inside the surface? There are a certain number of protons, all positively charged, and the exact same number of electrons, all negatively charged. Adding them all up creates a net charge of zero, which means no electric field. No electric field means the object as a whole is not charged.

The shielding of the outer electrons is known as Coulomb shielding. It is very important. When the balance of an atom is thrown off and it has more electrons than protons or more protons than electrons, the atom becomes charged. It is now called an ion. Ions are important in applications ranging from batteries to nerve cells. If ions were more common, the world would have a bigger electric field, which would make it difficult to operate electronic equipment, or even to walk around without getting shocked.