Roentgenium (Rg) is a synthetic element with the atomic number 111. It is highly unstable and radioactive, and as of my last update, only a few isotopes of roentgenium have been produced. The known isotopes of roentgenium include: 1. **Roentgenium-282 (Rg-282)**: This isotope has a half-life of approximately 2.1 milliseconds.

Rhodium (Rh) has several isotopes, but the most notable ones are: 1. **Rhodium-103 (Rh-103)**: This is the only stable isotope of rhodium and makes up nearly all naturally occurring rhodium. It has a nuclear spin of 1/2 and is commonly used in various applications, including catalytic converters and jewelry.

Rhenium (Re) is a transition metal with atomic number 75. It has several isotopes, but the most notable ones are: 1. **^185Re**: This is the most stable and abundant isotope of rhenium, with a half-life of approximately 4.0 × 10^10 years. It is a non-radioactive isotope and is commonly used in various applications, including catalysts and electronics.

Radon is a radioactive noble gas with the symbol Rn and atomic number 86. It has several isotopes, with the most notable being: 1. **Radon-222 (²²²Rn)**: The most stable and abundant isotope, with a half-life of about 3.8 days. It is produced naturally from the decay of uranium-238 and is significant in environmental studies due to its presence in soil and groundwater.

Radium has several isotopes, the most notable of which are Radium-226 and Radium-228. Here's a brief overview of these isotopes: 1. **Radium-226**: - It is the most stable and common isotope of radium. - It has a half-life of about 1,600 years and decays primarily through alpha decay into radon-222.

Protactinium (Pa) has several isotopes, but the most notable ones are: 1. **Protactinium-231 (Pa-231)**: This is the most stable and widely recognized isotope of protactinium. It has a half-life of about 32,760 years and is produced from the decay of uranium-235. It is used in various scientific research applications, including studies related to nuclear chemistry and geology.

Promethium (Pm) is a rare and radioactive element with the atomic number 61. It has a number of isotopes, most of which are unstable and radioactive. The most notable isotopes of promethium include: 1. **Promethium-145 (Pm-145)**: This isotope has a half-life of about 17.7 hours and decays into Neodymium-145.

Praseodymium, which has the atomic number 59, has several isotopes, with a total of 6 known isotopes ranging from \(\text{Pr}^{125}\) to \(\text{Pr}^{135}\). The most stable and naturally occurring isotopes of praseodymium are: 1. **Praseodymium-141 (\(^{141}\text{Pr}\))**: This is the most abundant isotope, constituting about 99.

Potassium has several isotopes, but the most notable ones are: 1. **Potassium-39 (⁴⁰K)**: This is the most abundant isotope, making up about 93.26% of natural potassium. It is stable and does not undergo radioactive decay. 2. **Potassium-40 (⁴⁰K)**: This isotope is radioactive and makes up about 0.012% of natural potassium. It has a half-life of approximately 1.

Polonium is a radioactive element with the symbol Po and atomic number 84. It has several isotopes, of which the most notable include: 1. **Polonium-210 (Po-210)**: This is the most well-known isotope of polonium. It has a half-life of about 138 days and is a potent alpha-emitter. Po-210 has been used in various research applications and has gained notoriety due to its use in poisoning cases.

Plutonium (Pu) has several isotopes, with the most notable being: 1. **Plutonium-238 (Pu-238)**: This isotope has a half-life of about 87.7 years and is used in radioisotope thermoelectric generators (RTGs) for powering spacecraft.

Platinum has several isotopes, the most stable and naturally occurring ones being: 1. **Platinum-194 (^194Pt)**: This is the most abundant natural isotope of platinum, making up about 32% of natural platinum. 2. **Platinum-195 (^195Pt)**: This isotope accounts for approximately 34% of natural platinum. 3. **Platinum-196 (^196Pt)**: About 25% of natural platinum is in the form of this isotope.

Phosphorus has several isotopes, but the most important ones are: 1. **Phosphorus-31 (\(^31P\))**: This is the only stable isotope of phosphorus and constitutes 100% of naturally occurring phosphorus. It has 15 protons and 16 neutrons. 2. **Radioactive isotopes**: Phosphorus also has several radioactive isotopes, which are produced in laboratory settings or through nuclear reactions.

Palladium (Pd) has a number of isotopes, but the most notable ones are: 1. **Palladium-102 (Pd-102)**: This is a stable isotope of palladium and makes up about 1.02% of natural palladium. 2. **Palladium-104 (Pd-104)**: This isotope is radioactive and has a half-life of about 3.1 hours. It decays primarily by beta decay.

Isotopes of oxygen are variants of the oxygen element that have the same number of protons (which is 8 for oxygen) but differ in the number of neutrons in their atomic nuclei. This difference in neutron number results in different atomic masses. The most common isotopes of oxygen are: 1. **Oxygen-16 (¹⁶O)**: This is the most abundant isotope, making up about 99.76% of natural oxygen.

Osmium (Os) is a chemical element with the atomic number 76, and it has several isotopes, both stable and radioactive. The most notable isotopes of osmium are: 1. **Stable Isotopes:** - **Os-184**: Has a natural abundance of about 0.02%. - **Os-187**: The most abundant stable isotope, constituting about 1.97% of osmium found in nature.

Oganesson (Og) is a synthetic element with the atomic number 118. It is a member of the noble gases group and is highly unstable, with a very short half-life. As of my last knowledge update in October 2023, only a few isotopes of oganesson have been identified, and they are primarily characterized by their mass numbers.

Nobelium (No) is a synthetic element with the atomic number 102. It has no stable isotopes, and its isotopes are all radioactive. The most commonly referenced isotopes of nobelium are: 1. **Nobelium-254 (No-254)**: This is the most stable isotope of nobelium, with a half-life of about 55 minutes.

Nitrogen has several isotopes, which are atoms of the same element (nitrogen) that have the same number of protons but different numbers of neutrons. The most common isotopes of nitrogen are: 1. **Nitrogen-14 (\(^14N\))**: This is the most stable and abundant isotope, making up about 99.6% of natural nitrogen. It has 7 protons and 7 neutrons.

Niobium (Nb) has several isotopes, but the two most significant ones are: 1. **Niobium-93 (³⁹Nb)**: This is the most stable and abundant isotope of niobium, comprising nearly 100% of naturally occurring niobium. It has a half-life that is effectively infinite in practical terms, and it does not undergo radioactive decay.