A free neutron is unstable and soon decays to other particles, one of them a proton. Must there be others? If so, what electric properties must they have?

The principle of conservation of charge is fundamental in physics, especially in processes involving subatomic particles. This law states that the total electric charge in an isolated system remains constant over time. In other words, charge can neither be created nor destroyed; it can only be transferred from one system to another.

Applying this to neutron decay, we must recognize that a neutron starts off as electrically neutral. Therefore, the cumulative charge of all decay products must sum to zero to respect charge conservation. Given that a proton, which has a positive electric charge, is one of the decay products, there must be other particles produced with equal and opposite charge to balance the equation. The decay path of a neutron typically includes an electron with a negative charge that exactly offsets the proton's positive charge, ensuring the total charge after decay remains zero.

Subatomic particles are the tiny constituents of an atom, predominantly the proton, neutron, and electron. Protons have a positive electric charge, electrons carry a negative charge, and neutrons are neutral. However, these are not the only subatomic particles. There are also neutrinos, like those produced in neutron decay, which are electrically neutral and very elusive due to their weak interactions with other forms of matter.

Understanding the behavior and properties of subatomic particles is essential for grasping fundamental physical processes, including radioactive decay. Each type of subatomic particle plays a distinct role, and their interactions are governed by the principles of quantum mechanics and the Standard Model of particle physics.

Electric charge is a fundamental property of matter. It is the physical property that enables one particle to exert an electric force on another. There are two types of electric charges: positive and negative. Like charges repel each other, whereas oppositely charged particles attract.

The unit of electric charge is the coulomb, and in terms of subatomic particles, the proton carries a charge of +1 (positive), whereas the electron carries a charge of -1 (negative). The neutrality of a neutron suggests that it has no net charge, but as we've seen in neutron decay, the process reveals the balanced production of charged particles – which is a beautiful demonstration of how nature preserves electric charge.