Nuclide

Everything is made of tiny bits.

These bits have centers. The centers have small parts inside. Some parts stay still. Some parts change.

These small parts are called protons and neutrons. The number of these parts tells us what the bit is. Some bits are stable. They stay the same for a long time. Other bits are not stable. They change into new things. This change is called decay. It can happen in space or in the ground. Watching how they change helps us learn about our world.

Every atom has a center called a nucleus.

Inside the nucleus are protons and neutrons. A nuclide is a specific type of atom. We name it by counting its protons and neutrons.

Scientists use different names for groups of nuclides. Isotopes have the same number of protons. Isotones have the same number of neutrons. Isobars have the same total weight. There are also nuclear isomers. These are atoms with the same protons and neutrons, but different energy levels.

Some nuclides are stable. This means they stay the same for a very long time. There are 251 stable nuclides in nature. Other nuclides are unstable. These are called radionuclides. They are radioactive. This means they go through decay. Decay is when they change into new things. Some radionuclides come from stars. Others are made by cosmic rays from space. Some are made by natural reactions in the ground. Tantalum-180m is a very special isomer. It lasts for a very long time. It has a life of more than 10^17 years.

Every atom has a tiny center called a nucleus.

A nuclide is a specific type of atom. We identify it by counting its protons and neutrons. We also look at its nuclear energy state. This tells us how much energy is inside the nucleus. The word nuclide was first used by Truman P. Kohman in 1947. He was an American nuclear physicist. He wanted a way to talk about the nucleus alone. This helped scientists separate nuclear traits from chemical traits.

Scientists use special names to group these atoms together. Isotopes are nuclides that have the same number of protons. Isotones are different because they have the same number of neutrons. Isobars are a group with the same total mass number. There are also isodiaphers, which have the same neutron excess. This means the difference between neutrons and protons stays the same. Mirror nuclides are very interesting too. They happen when the number of protons and neutrons are swapped.

Some atoms have the same protons and neutrons but different energy. These are called nuclear isomers. They are like the same type of atom but in a different state. One example is tantalum-180m. This is a very long-lived isomer. It lasts for more than 10^17 years. It is found naturally in the world. Other versions of tantalum decay much faster. For instance, tantalum-180 has a half-life of only 8 hours.

Nuclides can be stable or unstable. Stable nuclides do not change over time. There are 251 stable nuclides found in nature. Unstable nuclides are called radionuclides because they are radioactive. These undergo a process called decay. Some come from stars and formed long ago. We call these primordial radionuclides. There are 35 of these in nature. Others are made by cosmic rays from space. These are called cosmogenic nuclides.

Inside the nucleus, protons and neutrons stay together. They are held by a strong force. This force must overcome the electrical push between protons. As atoms get bigger, they need more neutrons to stay stable. For example, lead needs about 3 neutrons for every 2 protons. This helps keep the nucleus from breaking apart. Understanding these tiny parts helps us learn about the whole universe. It shows us how everything is built from the inside out.

A nuclide is a specific type of atom defined by its internal structure. Every atom has a nucleus at its center. A nuclide is characterized by three specific things: the number of protons (Z), the number of neutrons (N), and its nuclear energy state. While many people use the word "isotope" to describe these atoms, scientists often prefer the term "nuclide." This is because a nuclide focuses specifically on the properties of the nucleus itself.

The term was first coined in 1947 by an American nuclear physicist named Truman P. Kohman. He wanted a way to talk about the constitution of the nucleus independently from the chemical properties of the atom.

Understanding the difference between nuclides and isotopes is important for nuclear science. An isotope is a set of nuclides that all have the same number of protons. For example, carbon-13 is a nuclide with 6 protons and 7 neutrons. Because it has 6 protons, it belongs to the chemical element carbon. However, the number of neutrons can change the physical properties of an atom quite a bit. In very light elements like hydrogen and helium, the ratio of neutrons to protons changes significantly. This can even affect how biological systems work or how atoms behave at very low temperatures.

Scientists use several different names to group nuclides based on their shared characteristics. If nuclides have the same number of protons, they are called isotopes. If they have the same number of neutrons, they are called isotones. This name was created to show that the neutron number is the constant factor. When nuclides have the same mass number, which is the total sum of protons and neutrons, they are called isobars. There are also isodiaphers, which are nuclides that share the same neutron excess. This means the difference between their neutron count and proton count is equal.

Another fascinating group is known as mirror nuclides. These occur when the number of protons in one nuclide is equal to the number of neutrons in another, and vice versa. There are also nuclear isomers. These are nuclides that have the same number of protons and the same mass number, but they exist in different energy states. This means they are technically the same isotope, but they are different nuclides. A famous example is tantalum-180m. This is a long-lived nuclear isomer that can exist for more than 10^17 years. In contrast, the ground state of tantalum-180 is much less stable and decays in only 8 hours.

Nuclides are generally classified by their stability. There are 251 nuclides in nature that are considered stable and do not decay. These include 90 nuclides that are theoretically stable to all but proton decay. Unstable nuclides are called radionuclides because they are radioactive. These undergo a process called radioactive decay. There are about 701 natural radionuclides with half-lives longer than one hour. If a nuclide is created in a laboratory, it is called a synthetic nuclide. There are more than 4,000 of these known synthetic nuclides, many of which decay very quickly.

Natural radionuclides come from three main sources. The first group is called primordial radionuclides. These are remnants from the formation of the Solar System. They have half-lives longer than a small percentage of the age of the Earth. There are 35 identified primordial radionuclides, such as certain isotopes of uranium. The second group consists of radiogenic nuclides. These are "daughter" products created by the decay of other long-lived atoms. The third group is made through natural nuclear reactions. These can be cosmogenic nuclides, which are made by cosmic ray bombardment, or nucleogenic nuclides, which are made by neutron bombardment.

The stability of a nucleus depends on the balance of forces inside it. Protons are positively charged, so they naturally try to push each other away through electrical repulsion. To keep the nucleus together, neutrons are required to provide the residual strong force. This force binds the protons and neutrons together. As the number of protons increases, the nucleus needs a higher ratio of neutrons to stay stable. For example, light elements like calcium have an equal number of protons and neutrons. However, heavier elements like lead require about 3 neutrons for every 2 protons to remain stable.