out of total elements how many are natural? 95 98 100
Answers
Answer:
98
Explanation:
Of the 118 elements that have been discovered, there are 90 elements that occur in nature in appreciable amounts. Depending who you ask, there are another 4 or 8 elements that occur in nature as a result of radioactive decay of heavier elements. So, the grand total of natural elements is 94 or 98
Answer:
Elements 1 through 92 (except for elements 43 and 61) occur naturally on Earth, although some are only present in extremely small quantities.
Element 43, Technetium (Tc), is unstable, and all of its isotopes have relatively short half-lives, ranging from 4.2 million years (98Tc) to 5.0 seconds (108Tc). A half-life of 4.2 million years may sound like a long time, but since the Earth is 4.5 billion years old, all of the technetium that was originally present in the crust has decayed by now. Technetium has been detected in the corona of some stars, and can be produced artificially in kilogram quantities by the neutron bombardment of molybdenum-98, which forms technetium-99 by beta emission:
9842Mo + 10n —> 9942Mo —> 9943Tc + 0-1ß
Element 61, Promethium (Pm), is also unstable. The most stable isotope of the element, promethium-145, has a half-life of 17.7 years; promethium-146 has a half-life of only 5.53 years, while that of promethium-147 is 2.62 years. There are a number of other isotopes as well, but the majority of them have half-lives that are less than 30 seconds. Promethium is found in trace amounts in uranium ores, but because it is so unstable, it never accumulates above the concentration of about a picogram (10-12 g) per ton of ore. The spectral lines of promethium have also been observed in some stars. Promethium can be produced artificially by the bombardment of neodymium-146 with neutrons to form neodymium-147, which decays into promethium-147 and a beta particle:
14660Nd + 10n —> 14760Nd —> 14761Nd + 0-1ß
The elements following uranium on the periodic table are only produced artificially, and are known as the transuranium or transuranic elements. These elements may have existed on Earth early in its history, but like technetium, would have long ago decayed into more stable elements. These elements can be produced by several processes:
neutron bombardment causes an element to absorb a neutron, thereby becoming a heavier isotope of that element; if this heavier isotope is unstable, it may undergo beta decay, in which a neutron is converted into a proton, with the emission of a beta particle (ß, a high-speed electron ejected from the nucleus). The nucleus thus increases in atomic number by one unit:
10n —> 11p + 0-1ß
fusion of heavy elements with lighter elements such as hydrogen, helium, carbon, nitrogen, or oxygen can be made to occur in cyclotrons and particle accelerators; the particles are brought together with just enough energy to overcome the mutual repulsion of the positively-charged nuclei and cause the elements to fuse together, forming a heavier element in their place. Sometimes this process is referred to as cold fusion (this has no relationship to the infamous "unlimited energy" "fusion-in-a-jar" cold fusion debacle of the late-1980's). Some examples of this process are shown below:
24696Cm + 126C —> 254102No + 4 10n
20983Bi + 5826Fe —> 266109Mt + 10n
It has been theorized that the elements following element 112, which would be in the p-block region of the periodic table, might possibly be more stable than those of the last row of the transition metals (103-112); however, there is not as yet enough data to confirm whether this so-called "island of stability" actually exists. In any case, since only a few million or (at best) billion of the heaviest of these atoms can be produced at any one time, it is rather doubtful that any major construction projects will use any of these elements as building materials!
The table below lists the longest-lived isotopes of the transuranium elements, with their half-lives, discoverers, and method of production.*
Explanation:
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