Proton is defined as?

• A. A positively charged particle that, along with neutrons, comprise a nucleus.
• B. A negatively charged particle inside the nucleus.
• C. A neutral particle with mass equal to electron.
• D. A massless particle that binds atomic orbitals.

Answer: (A)

Protons are the positively charged constituents of the atomic nucleus, together with neutrons. They carry a +1 elementary charge and have a mass close to that of a neutron, about one atomic mass unit. The nucleus is made up of protons and neutrons, and the number of protons defines the atomic number, which determines the identity of the element. Protons are held in the nucleus by the strong nuclear force despite the repulsion between their positive charges. Electrons orbit the nucleus and are attracted to it by the electromagnetic force. This description matches the essential features of a proton: positive charge, location in the nucleus, and role in defining the element. The other statements fail because they describe a negatively charged particle inside the nucleus, a neutral particle with electron-like mass, or a massless particle that binds orbitals, none of which characterize a proton.