A chemical element is characterized by a particular number of protons in the nuclei of its atoms.

Although all the nuclei of all atoms belonging to one element will have the same number of protons, they may not necessarily have the same number of neutrons ; such atoms are termed isotopes.

In particle physics, a fermion ( a name coined by Paul Dirac from the surname of Enrico Fermi ) is any particle characterized by Fermi – Dirac statistics and following the Pauli exclusion principle ; fermions include all quarks and leptons, as well as any composite particle made of an odd number of these, such as all baryons and many atoms and nuclei.

Furthermore, as noted by Bohr, Moseley's law provided a reasonably complete experimental set of data that supported the ( new from 1911 ) conception by Ernest Rutherford and Antonius Van den Broek of the atom, with a positively-charged nucleus surrounded by negatively-charged electrons in which the atomic number is understood to be the exact physical number of positive charges ( later discovered and called protons ) in the central atomic nuclei of the elements.

Its four stable isotopes have 82 protons, a magic number in the nuclear shell model of atomic nuclei.

The liquid-drop model is able to reproduce many features of nuclei, including the general trend of binding energy with respect to mass number, as well as the phenomenon of nuclear fission.

For nuclei heavier than nickel-62 the binding energy per nucleon decreases with the mass number.

Some nuclei can capture a number of neutrons and remain relatively stable, not undergoing transmutation or decay for many months or even years.

Finally, the temperature gets high enough that any nucleus can be partially broken down, most commonly releasing an alpha particle ( helium nucleus ) which immediately fuses with another nucleus, so that several nuclei are effectively rearranged into a smaller number of heavier nuclei, with net release of energy because the addition of fragments to nuclei exceeds the energy required to break them off the parent nuclei.

As a gas is heated, electrons begin to leave the atoms, resulting in the presence of free electrons, which are not bound to nuclei, and ions, which are chemical species that contain unequal number of electrons and protons, and therefore possess an electrical charge.

In addition to its proximity to and association with the limbic system and the amygdala in particular, which plays a key role in emotional experience, the anterior cingulate cortex shares afferent and efferent pathways with a number of thalamic nuclei as well as the posterior cingulate and part of some parietal, frontal and supplementary motor cortex.

A few minutes afterward, starting with only protons and neutrons, nuclei up to lithium and beryllium ( both with mass number 7 ) were formed, but only in relatively small amounts.

Explosive nucleosynthesis occurs too rapidly for radioactive decay to decrease the number of neutrons, so that many abundant isotopes having equal even numbers of protons and neutrons are synthesized by the silicon quasiequilibrium set up in the explosive burning of oxygen and silicon, fusing nuclei that themselves have equal numbers of protons and neutrons to produce nuclides which consist of whole numbers of helium nuclei, up to 15 ( representing < sup > 60 </ sup > Ni ).

Note that the shells exist for both protons and neutrons individually, so that we can speak of " magic nuclei " where one nucleon type is at a magic number, and " doubly magic nuclei ", where both are.

room, chamber ) is a portion of the brain that contains a number of small nuclei with a variety of functions.

The below table contains various combinations of targets and projectiles which could be used to form compound nuclei with atomic number 116.

The stability of nuclei decreases greatly with the increase in atomic number after plutonium, the heaviest primordial element, so that all isotopes with an atomic number above 101 decay radioactively with a half-life under a day, with an exception of dubnium-268.

As S approaches T the square will be outside C and therefore both Af and Af must cross C an odd number of times as S varies from zero to T.

The Centimorgan is also often used to imply distance along a chromosome, but the number of base pairs it corresponds to varies widely.

The threshold is indexed biannually in March and September, and varies according to the number of dependants the bankrupt has.

The number of years varies depending on the company issuing the report, but the report will eventually cease to record that information.

The specific object varies with each game and can include taking as many tricks as possible, taking as many scoring cards ( or as few penalty cards ) within the tricks won as possible, taking as few tricks as possible, or taking an exact number of tricks.

Subfolders can contain still more files and folders and so on, thus building a tree-like structure in which one " master folder " ( or " root folder " — the name varies from one operating system to another ) can contain any number of levels of other folders and files.

The actual number in Scotland varies considerably — between approximately 350 to 500 due to the use of the term " island dun " for well over one hundred Hebridean examples — a distinction that has created a divide between mainland Scottish crannog and Hebridean islet settlement studies.

The number of Standing Committee members varies and has tended to increase over time.

The number of adherents to the various smaller groups of Christadelphians varies from approximately 1, 850 members ( the Unamended Christadelphians as of 2006 ) to groups made up of little more than one or two immediate families.

Chimpanzees mate throughout the year, although the number of females in estrus varies seasonally in a group.

The number of moults varies, both between species and genders, but generally will be between five times and nine times before the spider reaches maturity.

The number and definition of factors varies, depending on theoretical purpose, empirical emphasis, or school of economics.

The number of harp strings varies greatly, depending on the type of guitar and also the player's personal preference.

Accuracy on machine guns varies based on a wide number of factors from design to manufacturing tolerances, most of which have been improved over time.

For internal combustion engines in the form of jet engines, the power output varies drastically with airspeed and a less variable measure is used: thrust specific fuel consumption ( TSFC ), which is the number of pounds of propellant needed to generate impulses that measure a pound force-hour.

United States: In the United States the privately held company R. R. Bowker is the responsible entity, and there is a charge, which varies depending upon the number of ISBNs purchased, with prices ranging from $ 125. 00 for a single number.

The number of B channels for PRI varies according to the nation: in North America and Japan it is 23B + 1D, with an aggregate bit rate of 1. 544 Mbit / s ( T1 ); in Europe, India and Australia it is 30B + 1D, with an aggregate bit rate of 2. 048 Mbit / s ( E1 ).

The total number of Kashubians varies depending on one's definition.

The number of Rashad languages, also called Tegali – Tagoi, varies among descriptions, from two ( Williamson & Blench 2000 ), three ( Ethnologue ), to eight ( Blench ms ).

The species are not clearly distinct and estimates of the number of species varies from 13 to 18.

The number of mitochondria in a cell varies widely by organism and tissue type.

The number of rules observed varies with the order ; Theravada bhikkhus follow around 227 rules.

Mach number varies by the composition of the surrounding medium and also by local conditions, especially temperature and pressure.

Copernicus, by placing the sun at the center of the planetary universe, was able to reduce the number of epicycles from eighty-three to seventeen.

it involves a reduction in the number of epicycles from eighty-three to seventeen ''.

We did our job, Mr. Stavropoulos and Mr. De Seynes and myself, taking evidence from a number of people ''.

One serves society by conducting a business from which a certain number of employees draw their means of subsistence ; ;

The CTCA distributed a khaki-bound songbook that provided the impetus for spirited renditions of the selections found therein, plus a number of others whose lyrics were more earthy -- from `` Johnny Get Your Gun '' to `` Keep The Home Fires Burning '' to `` Mademoiselle From Armentieres ''.

But the attempt itself produced a number of brilliant works, and these form a transition from the early romantic period to the new age of Ibsen and Chekhov.

That Aristotelean-Thomistic principle experienced a thorough going-over from a number of the participants, but in the end the concept came to reassert itself.

and it is still very far from certain how valid the party's claim is that in `` a growing number of kolkhozes '' the peasants are finding it more profitable, to surrender their private plots to the kolkhoz and to let the latter be turned into something increasingly like a state farm.

Although a look of alarm passed over his face, he did not arrest his movements but disappeared into the shower room just as the chambermaid emerged from number nine.

The Navy, on April 25, announced it is bringing back the carrier Shangri-La from the Mediterranean, increasing to four the number of attack carriers in the vicinity of Cuba.

The Peace Corps can either begin in very low gear, with only preparatory work undertaken between now and when Congress finally appropriates special funds for it -- or it can be launched now and in earnest by executive action, with sufficient funds and made available from existing Mutual Security appropriations to permit a number of substantial projects to start this summer.

If your state has no provisions for the numbering of pleasure boats, you must apply for a number from the U.S. Coast Guard for any kind of boat with mechanical propulsion rated at more than 10 horsepower before it can be used on Federal waterways.

The number on the right of the symbol is always subtracted from the number on the left of the symbol.

Aside from the Ruger carbine, a number of hunting rifles have been introduced for the first time.

Reduces losses from stomach, hookworm, and nodular worms by interfering with reproduction of the female worm by reducing the number of eggs laid and essentially rendering all laid eggs sterile.

Are your expenses in this area commensurate with the number of employees who benefit from your program??

A number of semiempirical estimates by various workers lead to the conclusion that the Af bond becomes symmetric when the Af bond length is about 2.4 to 2.5 A, but aside from the possible example of nickel dimethylglyoxime there have been no convincing reports of symmetric Af bonds.

There may be a number of secondary effects resulting from diffusion through buildings such as widespread contamination of kitchens, restaurants, food stores, hospitals, etc..

Second, the upper portion permits comparison of maturity levels of an equal number of growth centers from the long, short, and round bones of the five regions.

It seems clear, from the counter-balanced shape of the series of arrows in Figure 5 that there was about an equal number of early and late Onsets and Completions for the 34 girls.

At the present time we do not know by what biochemical mechanism TSH acts on the thyroid, but for bio-assay of the hormone there are a number of properties by which its activity may be estimated, including release of iodine from the thyroid, increase in thyroid weight, increase in mean height of the follicular cells and increase in the thyroidal uptake of Af.

In litters of eight mice from similar parents, the number of mice with straight instead of wavy hair is an integer from 0 to 8.

More generally, suppose that an experiment consists of a number of independent trials, that each trial results in either a `` success '' or a `` non-success '' ( `` failure '' ), and that the probability of success remains constant from trial to trial.