What is a particle with a mass roughly equal to that of a proton, but no electrical charge?

A particle with a mass roughly equal to that of a proton and possessing no electrical charge is indeed a neutron. Neutrons are one of the primary constituents of atomic nuclei, along with protons, and they play a crucial role in the stability of atoms. They are classified as baryons, which are particles made up of three quarks.

Neutrons are essential in nuclear reactions and contribute to the overall mass of an atom, but they do not carry an electric charge, which distinguishes them from protons that are positively charged and electrons that are negatively charged. Understanding the role of neutrons helps in grasping concepts related to atomic structure and nuclear physics.

The other options are distinct in their properties: an electron has a negative charge and a much smaller mass compared to protons and neutrons, a photon is a massless particle that carries electromagnetic force, and a positron is the antimatter counterpart of the electron, carrying a positive charge. Each of these characteristics makes them unsuitable as the answer to the question regarding a neutral particle with mass comparable to that of a proton.