Which symbol represents a positron particle?

Which symbol represents a positron particle?

• A. ₂⁴He
• B. ₀¹n
• C. ₁¹H
• D. +₁⁰e

Answer: (D)

A positron is the antiparticle of the electron: it has the same mass as an electron but a positive charge. In particle notation, leptons like electrons and positrons are shown with a symbol e and a sign for charge; the positron appears as a positively charged e with essentially zero nucleon content (mass number and baryon number are effectively zero). The symbol that shows a plus sign in front of e, with no nucleons included, identifies this as a positron. The other symbols correspond to nucleons or nuclei: a helium-4 nucleus is an alpha particle with mass number 4 and charge +2; a neutron has no charge and a mass number of 1; a hydrogen-1 nucleus is a proton with mass number 1 and charge +1. These are not leptons, and they carry nonzero mass numbers, so they are not positrons.

A positron is the antiparticle of the electron: it has the same mass as an electron but a positive charge. In particle notation, leptons like electrons and positrons are shown with a symbol e and a sign for charge; the positron appears as a positively charged e with essentially zero nucleon content (mass number and baryon number are effectively zero). The symbol that shows a plus sign in front of e, with no nucleons included, identifies this as a positron.

The other symbols correspond to nucleons or nuclei: a helium-4 nucleus is an alpha particle with mass number 4 and charge +2; a neutron has no charge and a mass number of 1; a hydrogen-1 nucleus is a proton with mass number 1 and charge +1. These are not leptons, and they carry nonzero mass numbers, so they are not positrons.