Tag: Nucleus

Electric Charge is not the only type of Fundamental Charge

Super fact 59 : Most people have heard of electrical charges, positive and negative. However, in nature there are also color charges—red, green, and blue—which are analogous to electric charges. In addition, there are anti-red, anti-green, and anti-blue charges.

Esther’s writing prompt: 10th September : Charge

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As you may know, atoms consist of particles. Electrons surround the nucleus of the atom. The nucleus of the atom is in the middle of the atom and it consists of protons and neutrons. Electrons have a negative charge. Protons have a positive charge. Neutrons do not have an electrical charge. Electrons are so called elementary particles. They are not composed of other particles. Protons and Neutrons, on the other hand, are not elementary particles. They are composite particles consisting of quarks, gluons and quark pairs called mesons.

The picture shows a Hydrogen atom consisting of one proton and one electron, one Carbon atom with six electrons, six protons and six neutrons, an Oxygen atom with eight electrons, eight protons and eight neutrons, and a Nitrogen atom with seven electrons, seven protons and seven neutrons | Electric Charge is not the only type of Fundamental Charge
Four elements with a nucleus and electron shells. The number of electrons, protons, and neutrons is shown. The green particles circling the nucleus are electrons. The red particles in the nucleus (middle) are protons and the blue particles in the nucleus are neutrons. The colors of the particles in this picture have nothing to do with color charges. The four elements are Hydrogen, Carbon, Oxygen, and Nitrogen. There are 118 elements. These elements can combine into millions of different kinds of molecules that make up everything. Asset id: 1555863596 by OSweetNature.

Quarks have electric charges, just like an electron and a positron, which is why a proton has an electric charge, a positive electric charge. However, in addition quarks have something called color charge. Unlike electric charges, which come in two forms, negative and positive, they come in three forms red, green and blue and in anti-red, anti-green, and anti-blue (well six forms actually). I should say that the color charges, red, green and blue, are not real colors. They are just names. Just electric charges are associated with electric forces; color charges are associated with the nuclear strong force. The strong force is even stronger than the electrical force.

If you take an equal amount of positive and negative electric charges you get something that is electrically neutral. If you take an equal amount of red, green and blue you get what is called white, or neutral. If you take an equal amount of red and anti-red you also get white. Any other mix gives you a net color charge.

vector illustration of up and down quarks in proton and neutron on white background. The proton (left) is a red and blue up quark and a green down quark. The neutron is a red and green down quark and a blue up-quark.
The proton and neutron each consist of three quarks. Protons consist of two up quarks and one down quark. Neutrons consist of two down quarks and one up quark. Both protons and neutrons have a net white charge. The yellow squiggly lines are gluons transporting color charge between the quarks. Asset id: 2333679305 by KRPD.

I can add that gluons are elementary particles that in many respects are like photons. Light consists of photons. It is because of the photons that we can see. In addition, the photons transport electrical charge. Photons are massless elementary particles with the intrinsic spin of one, and they belong to a group of elementary particles called Bosons. Gluons transport color charge, and they are massless and have an intrinsic spin of one and belong to the same group of elementary particles called Bosons. Unlike photons, they are stuck inside the nucleus and unlike photons they never get to see the light of day. The pun was intended.

Matter, light, and electrical charges are all part of our daily life. We can touch matter, see light, and we come across electrical charge when we touch something that is charged or when we see lightning. However, we do not come across quarks, gluons, and color charges in our daily life because they are hidden at the center of the atoms. Yet they are fundamental to the existence of matter, of us. We know color charges exist, the existence of color charges is an important fact, and yet it is not a well-known fact and often a big surprise to people. Therefore, I think it is a super fact.

The 118 Elements and the 3,500 Isotopes

There are 118 known elements. Why not 500, or just 4 or 5, like the ancient Greeks believed? Each element is defined by it having a certain number of protons and the same number of electrons if it is to be electrically neutral. The problem with having more than one proton in the nucleus is that protons all carry a positive charge and therefore want to push each other away. Same charges repel and different charges attract. What saves the nucleus from blowing apart are the neutrons and the associated strong nuclear force (protons & neutrons) which is guided by the color charges. The quantum model for electricity is called Quantum electrodynamics or QED. The quantum model for color charges is called Quantum chromodynamics or QCD.

As you add more protons it becomes increasingly more difficult for the nuclear forces (strong and weak) to hold the nucleus together. The positive charge of the protons is pushing too hard. That’s why there are only 118 Elements. Another thing to note is that the number of neutrons does not have to be the same as the number of protons. This means that for each element there are several kinds of so-called isotopes. For example, carbon has six protons and six electrons (if the atom is electrically neutral) but the carbon atom / element can have six neutrons, seven neutrons, or eight neutrons. You call them carbon-12, carbon-13, and carbon-14, where the number represents the number of protons plus the number of neutrons.

The picture shows a Carbon-12 isotope, a Carbon-13 isotope, and a Carbon-14 isotope | Electric Charge is not the only type of Fundamental Charge
Three natural isotopes of Carbon Stock Vector ID: 2063998442 by zizou7
Bohr model representation of the uranium atom, number 92 and symbol U. Conceptual vector illustration of uranium-238 isotope atom, mass number 238 and electron configuration 2, 8, 18, 32, 21, 9, 2.
This is a simplified Bohr model of the Uranium atom. There are 92 little blue balls circling a nucleus in the middle of the atom. Those are electrons. In the nucleus there are 92 protons. Those are the red balls with plus signs. In addition, there is a yellowish smudge around the protons in the nucleus. Those are the neutrons. Depending on the isotope, there are 143 neutrons for U-235, 146 neutrons for U-238 and 142 neutrons for U-234. Shutterstock asset id: 1999370450 by Patricia F. Carvalho

It is the electrons that determine the chemical properties of an element, and therefore isotopes with a different amount of neutrons are chemically identical. However, they are different with respect to properties that relate to he nucleus, such as radioactivity/stability, and of course weight. Also, when atoms combine into molecules their chemical properties change drastically, but again that is due to the rearrangement of the electrons. There are around 3,500 known isotopes, most of them radioactive.

What is a Quark?

To learn more about Protons, Neutrons, Quarks, Gluons, Color Charges, and Quantum Chromodynamics you can watch this 10 minute video below.

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There is a lot of Uranium in your Backyard

Super fact 49 : The top one-meter (3.3 feet) of a typical 10 meters (33 feet) by 40 meters (131 feet) garden contains 2 kilograms (4.4 pounds) of Uranium. For comparison, the Hiroshima bomb contained 64 kilograms (121 pounds) of Uranium. Certain rocks such as Granite and Shale contain much more Uranium than soil. Uranium also exists in the atmosphere and there is 4.5 billion tons of Uranium in the ocean.

The numbers above come from the IAEA (International Atomic Energy Agency) and Stanford University . I should mention that the numbers vary depending on Geography, type of soil, etc. For example, there is much less Uranium in the soil in Florida compared to the soil in the Midwest.

This may come as a surprise to many people. Isn’t Uranium radioactive? How come we are still alive? That’s why I call this a super fact. The answer is that even though Uranium is used in nuclear bombs and nuclear reactors, it is by itself not very radioactive. You can hold natural uranium in your hand without much risk. The radioactivity from, for example, nuclear explosions come mainly from the fission process and the radioactivity from nuclear reactor waste is mainly from other isotopes created by the fission process in the reactor rather than the uranium itself.

An enormous nuclear bomb explosion in the dessert featuring a huge mushroom cloud | There is a lot of Uranium in your Backyard
If Uranium is not very radioactive, how come a nuclear bomb spread so much radioactivity. The answer is that the radioactivity comes from the fission process and the resulting new isotopes, not the uranium.

What Are Isotopes?

Before I explain some facts about the radioactivity and decay rate of Uranium, I should explain what an isotope is. Atoms consist of a nucleus and electrons surrounding the nucleus. In the nucleus there are protons and neutrons (and some other stuff). Neutral atoms have an equal amount of electrons and protons, which determines what kind of element it is. Hydrogen has one electron and one proton. Helium has two electrons and two protons. Oxygen has eight electrons and eight protons, etc. The number of protons/electrons is called the atomic number of the element.

The number of protons plus the number of neutrons is called the mass number. Atoms of the same element but different number of neutrons are called isotopes. Uranium-235 or U-235 has 92 protons and 235 – 92 = 143 neutrons. The number if protons/electrons determine the chemical properties of the element. The number of neutrons determines nuclear properties such as the stability of the nucleus, radioactivity, etc., as well as the weight. Therefore U-238 and U-235 are identical chemically and look and feel the same, but U-235 is more radioactive, and you can use U-235 for fission but not U-238.

Bohr model representation of the uranium atom, number 92 and symbol U. Conceptual vector illustration of uranium-238 isotope atom, mass number 238 and electron configuration 2, 8, 18, 32, 21, 9, 2
This is a simplified Bohr model of the Uranium atom. There are 92 little blue balls circling a nucleus in the middle of the atom. Those are electrons. In the nucleus there are 92 protons. Those are the red balls with plus signs. In addition, there is a yellowish smudge around the protons in the nucleus. Those are the neutrons. Depending on the isotope, there are 143 neutrons for U-235, 146 neutrons for U-238 and 142 neutrons for U-234. Shutterstock asset id: 1999370450 by Patricia F. Carvalho

The decay rate of Uranium

There are three main Uranium isotopes. Uranium-234, Uranium-235, and Uranium-238. Uranium-238 is the most common. 99.28% of natural Uranium is Uranium-238, 0.72% is Uranium-235 and 0.0057% is Uranium-234. Uranium-235 is the isotope we use for nuclear weapons.

The different isotopes have different decay rates and different levels of radioactivity. The half life of a radioactive isotope is the time it takes for an isotope to decay so that only half of it is left. The half-life of Uranium-238 is four and half billion years. That means that it will be around for a very long time, but since its decay rate is so slow, it is not very radioactive. The half-life of Uranium-235 is 710 million years, again it will be around for a very long time, but again, since its decay rate is so slow, it is not very radioactive. The half-life Uranium-234 is 247,000 years, a little bit faster but it still has a pretty slow decay rate.

This should be compared to Cesium-137, which has a half-life of roughly 30 years. In other words, it decays 150 million times faster than Uranium-238 and 23.7 million times faster than Uranium-235. Since Cesium-137 decays so much faster than the Uranium isotopes it means that each atom of Cesium-137 will send out radioactive particles much more often than a Uranium atom will, making it much more radioactive.

If you want to read about when I was walking around a whole day with a Cesium-137 sample in the back pocket of my jeans, click here. Radon-222, an extremely radioactive isotope of radon, which seeps into our basements from the inside of earth. It has a half-life of 3.82 days giving it a decay rate that is 430 billion times faster than Uranium-238 and 68 billion times faster than Uranium-235.

What makes it possible to make a nuclear bomb from Uranium-235 is not because it is very radioactive. It is not. It is because it has properties that make it perfect for bomb making. Each nucleus emits more than one neutron, in fact more than two on average, and the neutrons colliding with other Uranium-235 nucleuses can be made to travel at the correct speed to cause fission. In other words, it is fissile. It is a goldilocks situation. It is just right. Below is an illustration showing a chain reaction. Observe, the picture indicates that Uranium has 95 protons. This is wrong. Uranium has 92 protons. When I have the time, I will fix this picture.

Illustration of nuclear chain reaction. Uranium-235 fission | There is a lot of Uranium in your Backyard
This is an illustration of a chain reaction with fission of a Uranium-235 isotope. Notice the atomic number (number of protons) is incorrectly stated as 95 in the picture. It is 92.  When I have time, I will fix that. Shutterstock Asset id: 73714504 by Mpanchenko.

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