In the periodic table of elements, elements No. 43, elements No. 61 and all elements after No. 83 are radioactive elements, and these elements will decay. In short, it is to change from one element to another element. So why does it change? There are currently 118 types of elemen

In of the periodic table of elements, element 43, element 61 and all elements after 83 are radioactive elements , and these elements will undergo decay . In short, it is to change from one element to another element. So why does it change?

Currently, there are 118 types of elements known to humans, including both radioactive and non-radioactive elements. Whether an element is radioactive depends entirely on its internal structure. Any element is composed of atomic nucleus and electrons outside the nucleus. The electrons are fermion , which is the elementary particle, and cannot be separated. There are protons and neutrons in the nucleus. The number of protons and neutrons in the nucleus of different elements is different. The number of protons in the nucleus determines what element it is. For example, the one that has one proton is the hydrogen atom , and the one that has two protons is the helium atom .

The number of protons determines the type of element, and the number of neutrons determines what kind of isotope it is.

For example, hydrogen has three isotopes, with a ratio of hydroxide, deuterium and tritium. hydroxide has only 1 proton, but no neutron. Deuterium has 1 proton and 1 neutron, while tritium has 1 proton and 2 neutrons. Among the three isotopes of hydrogen, only tritium is radioactive and has a relatively strong radioactivity, because the shorter the half-life of a radioactive element, the more radioactivity it produces per unit time, while the half-life of tritium is only 12.4 years. Now we can basically vaguely feel that the radioactivity of elements seems to be related to the number of protons and neutrons. Yes, that's true. Now let’s think about a question: what makes protons and neutrons combine to form a nucleus? It's powerful.

There are four types of basic forces in our world, namely strong force, weak force, electromagnetic force and gravity. Among them, the strongest force is the strongest and the gravity is the weakest. How powerful is

? Although protons and neutrons are small, they are not elementary particles. Although they are not elementary particles, we do not have the ability to further split them. Why? Because protons are composed of three quarks and , and what makes the three quarks combine together is strength, this combination that relies on strong forces to combine together cannot knock it away even if it is a high-energy particle collider, and its power is obvious. Quarks combine into protons due to their strength. Similarly, the ones that bind protons and neutrons are also strong, so it is not easy to separate them. However, there is not only a powerful force in the atomic nucleus, but also another kind of force.

Another force in the nucleus is electromagnetic force.

Electromagnetic force exists as a "repulsive force" in the nucleus, because all protons are positively charged, and there are so many protons in the nucleus, so naturally there will be repulsion between each other. However, for most atoms , this repulsion force inside the nucleus will not affect the stability of the nucleus, because the electromagnetic force is much weaker than the strong force. However, although the electromagnetic force is weak, it is a long-range force. Although the strong force is strong, it is a short-range force. The action distance of the strong force is only 10-15 square meters. What does this mean? This means that within the nucleus, because the action distance is long, electromagnetic force can be superimposed, while strong forces with very short action distance can only do their own affairs.

The strong force in the nucleus will not change, but the electromagnetic force opposite it will increase due to the increase of the number of protons. Therefore, when the number of protons in the nucleus reaches enough, the electromagnetic force can compete with the strong force.

When the electromagnetic force in the nucleus is large enough to counter strong forces, the contradictions within the nucleus will reach an irreconcilable level, and the nucleus will become extremely unstable at this time. Unstable is definitely not possible, so how can we restore stability? It's very simple, invite the troublemakers out, that is, throw out a few protons and neutrons. This is decay.It is easy to understand to throw protons and neutrons out to maintain stability, but why are the number of protons and neutrons thrown out when a radioactive element decays? What determines how many protons and neutrons should be thrown out?

In imagination, protons and neutrons in the nucleus should be evenly distributed, but in fact it is not.

The protons and neutrons in the nucleus exist in the form of agglomerations, and the easiest group to form is the alpha group, that is, two protons and two neutrons. Therefore, when an element throws an α group outward, it will cause an α decay , reducing two protons and two neutrons. For example, after α decay occurs, uranium 238 will become thorium 234. The isotope tritium of hydrogen will convert one neutron into a proton when decayed, so the tritium of 1 proton and 2 neutron will decay into helium3 3 of 2 proton and 1 neutron, which is called β decay . It should be noted that decay is a random event. Any radioactive element may decay in the next second, or it may decay after 1 billion years. As for the half-life, what it describes is only a probability. It’s like there is an element with a half-life of 10 years. When we have many such elements, we will observe that about half of the elements will decay after 10 years, but as for a single element, it is normal that it does not decay for 100 years.