Final answer:
The positively charged subatomic particle in atomic nuclei is known as a proton. Protons, along with neutrons, make up the nucleus of an atom, while electrons orbit around the nucleus.
Step-by-step explanation:
A positively charged subatomic particle that exists in atomic nuclei is called a proton. This particle, along with neutrons, constitutes the nucleus of an atom. Protons have a positive electric charge, and their presence in the nucleus gives it a positive charge overall.
Other subatomic particles, such as electrons, carry a negative charge and orbit the nucleus, while neutrons are neutral in charge. Together, the protons, neutrons, and electrons make up an atom. The discovery of the proton as a constituent of the atomic nucleus was a significant milestone in the field of Chemistry, helping us understand the structure of matter at a very fundamental level.