Chlorine is a chemical element with atomic number 17 which means there are 17 protons and 17 electrons in the atomic structure. Before a name and symbol are approved, an element may be referred to by its atomic number (e.g., element 120) or by its systematic element name. The systematic element name is a temporary name that is based on the atomic number as a root and the -ium ending as a suffix. For example, element 120 has the temporary name unbinilium. Atom - Atom - Atomic bonds: Once the way atoms are put together is understood, the question of how they interact with each other can be addressed—in particular, how they form bonds to create molecules and macroscopic materials. There are three basic ways that the outer electrons of atoms can form bonds: The first way gives rise to what is called an ionic bond. Consider as an example an atom.

Atomic Number = 17 Atomic Weight = 35.4527 Reference E95: Isotope: Mass: Abundance: Spin: Mag Moment: 35 Cl: 34.968852: 75.77%: 3/2 +0.82187: 37 Cl: 36.965903: 24.23%: 3/2 +0.68412: Cl I Ground State 1s 2 2s 2 2p 6 3s 2 3p 5 2 P. Element Chlorine (Cl), Group 17, Atomic Number 17, p-block, Mass 35.45. Sources, facts, uses, scarcity (SRI), podcasts, alchemical symbols, videos and images.

In 1961, the Commission recommended A_r(Cl) = 35.453(1), based on the atomic weight ofsilver and on Ag/AgCl equivalent ratios determined chemically by many well-known authorities.Following its 1967 discussion of Ag, Cl, and Br, which were important in the chemical determinationof atomic weights of several other elements, the Commission did not assign any new atomic-weight valuesdefined purely on the basis of chemical measurements.

Since 1985, relative isotope-ratio mass spectrometry has yielded abundant evidence for variability in theatomic weight of chlorine in both natural and artificial substances, which resulted in the 1999 decisionto increase the uncertainty and remove a significant figure from the atomic weight of chlorine, and to introduce the interval notation in 2009.

The basis of the delta scale for relative Cl isotope-ratiomeasurements currently is standard mean ocean chloride (SMOC), with δ³⁷Cl = 0 ‰, despite reportedevidence for variability in n(³⁷Cl)/n(³⁵Cl) of seawater chloride.

Cl Atomic Number

Chlorine isotopes in the chloride ion may be fractionated in nature and the laboratory by diffusion,ion filtration, and halide mineral precipitation. The lighter isotope ³⁵Cl diffuses more rapidly inaqueous solutions, whereas the concentration of the heavier isotope ³⁷Cl is higher in halide mineralsthan in coexisting solutions. Chlorine isotopes also have been fractionated photochemically in the laboratory. Environmental chloride samples are reported to have δ³⁷Cl values ranging from about−7.7 ‰ to +7.5 ‰, corresponding to x(³⁷Cl) = 0.2408 to 0.2436 and A_r(Cl)= 35.450 to 35.455.

Chlorinated organic solvents from different commercial sources commonlyhave different Cl isotopic compositions. The chlorine isotopes of those compounds may also be fractionatedby biochemical degradation reactions. Chlorinated solvents are reported to have δ³⁷Cl values rangingfrom at least −6.0 ‰ to +4.4 ‰, corresponding to x(³⁷Cl) = 0.2411 to 0.2430 andA_r(Cl) = 35.450 to 35.454. The range of Cl atomic weights in nature and in laboratory reagents is largerthan the range indicated by the standard atomic-weight uncertainty value. Larger ranges of variation may be found as measurements are made on a wider range of environmentsand of Cl-bearing species.

The radioactive isotope ³⁶Cl decays to ³⁶Ar with a half-life of 301(2) ka. It is produced bothnaturally and artificially by slow-neutron reactions with ³⁵Cl. Large quantities of ³⁶Cl were injected intothe atmosphere as a by-product of nuclear bomb tests in the oceans. Both natural cosmogenic ³⁶Cl andbomb-produced ³⁶Cl from the atmosphere have been useful as environmental tracers in hydrologic studies; however, the concentrations normally encountered are too low by several orders of magnitudeto have a measurable effect on the atomic weight of chlorine.

CIAAW

Chlorine
A_r(Cl) = [35.446, 35.457] since 2009
The name derives from the Greek chloros for 'pale green' or 'greenish yellow' colour of the element. Itwas discovered by the Swedish pharmacist and chemist Carl-Wilhelm Scheele in 1774. In 1810, theEnglish chemist Humphry Davy proved it was an element.

Natural variations of chlorine isotopic composition

Cl Atomic Numbers

Isotopic reference materials of chlorine.