In general, the half-life becomes shorter as atomic number increases, though an " island of stability " may exist for undiscovered isotopes with certain numbers of protons and neutrons.

Antimony exists as two stable isotopes, < sup > 121 </ sup > Sb with a natural abundance of 57. 36 % and < sup > 123 </ sup > Sb with a natural abundance of 42. 64 %.

All of its isotopes are short-lived ; the most stable is astatine-210, with a half-life of 8. 1 hours.

Six astatine isotopes, with mass numbers of 214 to 219, are present in nature as the products of various decay routes of heavier elements, but neither the most stable isotope of astatine ( with mass number 210 ) nor astatine-211 ( which is used in medicine ) is produced naturally.

All other nuclides ( isotopes of hydrogen and all other elements ) have more nucleons than electrons, so the fraction of mass taken by the nucleus is closer to 100 % for all of these types of atoms, than for hydrogen-1 .</ ref > with protons and neutrons having roughly equal mass.

The explanation for these different isotopes awaited the discovery of the neutron, a neutral-charged particle with a mass similar to the proton, by the physicist James Chadwick in 1932.

In practice, this mode of decay has only been observed in nuclides considerably heavier than nickel, with the lightest known alpha emitter being the lightest isotopes ( mass numbers 106 – 110 ) of tellurium ( element 52 ).

About twenty isotopes and six nuclear isomers ( excited states of an isotope ) of berkelium have been characterized with the atomic numbers ranging from 235 to 254.

The isotope effect was reported by two groups on the 24th of March 1950, who discovered it independently working with different mercury isotopes, although a few days before publication they learned of each other's results at the ONR conference in Atlanta, Georgia.

There are three naturally occurring isotopes, with < sup > 12 </ sup > C and < sup > 13 </ sup > C being stable, while < sup > 14 </ sup > C is radioactive, decaying with a half-life of about 5, 730 years.

Some of these elements, notably thorium ( atomic number 90 ) and uranium ( atomic number 92 ), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our solar system.

Certain elements have no stable isotopes and are composed only of radioactive isotopes: specifically the elements without any stable isotopes are technetium ( atomic number 43 ), promethium ( atomic number 61 ), and all observed elements with atomic numbers greater than 82.

Of the 80 elements with at least one stable isotope, 26 have only one stable isotope, and the mean number of stable isotopes for the 80 stable elements is 3. 1 stable isotopes per element.

Some of these elements, notably thorium ( atomic number 90 ) and uranium ( atomic number 92 ), have one or more isotopes with half-lives long enough to survive as remnants of the explosive stellar nucleosynthesis that produced the heavy elements before the formation of our Solar System.

Naturally occurring chromium is composed of three stable isotopes ; < sup > 52 </ sup > Cr, < sup > 53 </ sup > Cr and < sup > 54 </ sup > Cr with < sup > 52 </ sup > Cr being the most abundant ( 83. 789 % natural abundance ).

Among the isotopes that do not occur naturally, the most long-lived are < sup > 109 </ sup > Cd with a half-life of 462. 6 days, and < sup > 115 </ sup > Cd with a half-life of 53. 46 hours.

Brannon was hunkered down with his broad back to the left rear wheel, with the other two facing him.

The code, which had probably something to do with sex or some other interest, Nicolas was determined to find out and put to use.

Thirty minutes later, the outrigger grated on sand and other girls, waiting on shore, rushed forward to pull it up on the beach and make it fast with vine ropes to a large boulder.

In the other: a wristwatch with broken crystal wrapped in a dirty handkerchief.

In the caves, with other supplies, they had kept cases of sake.

He saw the most action, beat up more badmen with his bare fists, broke up the most gangs and sent more murderers to the gallows than any other U.S. marshal who lived before or after him.

At noontime, remembering what the teacher had said about maybe playing with the kids, Jack stayed close to the schoolhouse while all the other big boys, except Charles, went off out the road to play ball.

With one hand she held her skirt down while she took Jack's extended hand with the other.

Among Bourbons the racial issue may have less to do with their remaining unreconstructed than other factors.

Thus, to cite but one example, the Pax Britannica of the nineteenth century, whether with the British navy ruling the seas or with the City of London ruling world finance, was strictly national in motivation, however much other nations ( e.g., the United States ) may have incidentally benefited.

A system of `` gold '' -- actually yellow -- phones connects him with the offices and action stations of the Secretary of Defense, the Joint Chiefs of Staff, the SAC commander and other key men.

Those three other great activities of the Persians, the bath, the teahouse, and the zur khaneh ( the latter a kind of club in which a leader and a group of men in an octagonal pit move through a rite of calisthenics, dance, chanted poetry, and music ), do not take place in buildings to which entrance tickets are sold, but some of them occupy splendid examples of Persian domestic architecture: long, domed, chalk-white rooms with daises of turquoise tile, their end walls cut through to the orchards and the sky by open arches.

As more and more Jewish musicians lost their jobs with professional organizations Steinberg united them into the Frankfurt Kulturbund Orchestra, which also gave guest performances in other German cities.

Strong men with strong opinions, frank to the point of being refreshingly indiscreet, the Founding Seven were essentially congenial minds, and their agreements with each other were more consequential than their differences.

The effects of television and other mass media are erasing regional dialects and localisms with a startling force.

Yet he presents a realm of source material which may well serve other writers if not himself: the problems with which a New South must grapple in groping through a blind adolescence into the maturity of urbanization.

For the family is the simplest example of just such a unit, composed of people, which gives us both some immunity from, and a way of dealing with, other people.

This and other fears of the solar system have disappeared gradually, first, with the Ptolemaic system and its built-in concept of periodicity and then, more firmly, with the Newtonian innovation of an universal force that could account quantitatively for both terrestial and celestial motions.

Two thieves are crucified with Christ, one saved and the other damned.

As Lipton puts it: `` The Eros is felt in the magic circle of marijuana with far greater force, as a unifying principle in human relationships, than at any other time except, perhaps, in the mutual metaphysical orgasms.

In any social system in which communications have an importance comparable with that of production and other human factors, a point like f in Figure 2 would ( other things being equal ) be the dwelling place for the community leader, while e and h would house the next most important citizens.

He had braved the elements and the enemy, but the strain, aided by the winter, was catching up with him at last.

And they have done this on a very large scale, with a veritable flood of novels and stories which are either dystopias or narratives of adventure with dystopian elements.

The novels and stories like Pohl's Drunkard's Walk ( 1960 ), with the focus on adventure and with the dystopian elements only a dim background -- in this case an uneasy, overpopulated world in which the mass of people do uninteresting routine jobs while a carefully selected, university-trained elite runs everything -- are in all likelihood as numerous as dystopias.

They are the result of a constant and careful contest with the elements.

By the time the child first attacks the actual problem of reading, he is completely familiar and at ease with all of the elements of words.

In considering roleplaying for analysis we enter a more complex area, since we are now no longer dealing with a simple over-all decision but rather with the examination and evaluation of many elements seen in dynamic functioning.

Proponents of single elements tend to ensure predominance of that element without determining if it is justified, and the element with the most enthusiastic and vociferous proponents has assumed the greatest importance.

Thus, the combined efficiency of the elements replaced by the two fiber plates ( with a combined efficiency of 0.25 ) is 0.043 or about six times less than that of the two fiber plates.

very old red wine is often decanted so that the puckering, bitter elements which have settled to the bottom will not be mingled with the wine itself.

Now time is also the concern of the fictional narrative, which is, at its simplest, the story of an action with, usually, a beginning, a middle, and an end -- elements which demand time as the first condition for their existence.

When, therefore, it turned its attention to the concrete entities with which popular imagination had peopled the world of spirit, these entities soon lost whatever status they had enjoyed as actual elements of external reality.

" However, as Stocking notes, Tylor mainly concerned himself with describing and mapping the distribution of particular elements of culture, rather than with the larger function, and he generally seemed to assume a Victorian idea of progress rather than the idea of non-directional, multilineal cultural development proposed by later anthropologists.

Toward the turn of the twentieth century, a number of anthropologists became dissatisfied with this categorization of cultural elements ; historical reconstructions also came to seem increasingly speculative to them.

Polykleitos in his Canon wrote that beauty consists in the proportion not of the elements ( materials ), but of the parts, that is the interrelation of parts with one another and with the whole.

And its complete meaning was taken as: counting with small similar elements by somebody.

The alkali metals are a group of chemical elements in the periodic table with very similar properties: they are all shiny, soft, silvery, highly reactive metals at standard temperature and pressure and readily lose their outermost electron to form cations with charge + 1.

The alkali metals provide the best example of group trends in properties in the periodic table, with elements exhibiting well-characterized homologous behaviour.

Experiments have been conducted to attempt the synthesis of ununennium ( Uue ), which is likely to be the next member of the group, but they have all met with failure .< ref name =" link "> However, ununennium may not be an alkali metal due to relativistic effects, which are predicted to have a large influence on the chemical properties of superheavy elements.

This placement is consistent with the modern practice of ordering the elements by proton number, Z, but this number was not known or suspected at the time.