Chlorine-35

Properties and data of the isotope ³⁵Cl.

Contents

Chlorine-35 is a naturally occurring, stable isotope of the chemical element chlorine, which, in addition to the element-specific 17 protons, has 18 neutrons in the atomic nucleus, resulting in the mass number 35 ; the proportion of earthly chlorine is 75.8%. Isotopically pure ³⁵Cl is obtained from conventional chlorine and is used, among other things, to produce Chlorine-36, a radioisotope that is used in research.

The nuclide ³⁵Cl acts as a neutron absorber with a relatively high capture cross section for thermal neutrons of 44 barn. The natural chlorine isotope mixture of Cl-35 and Cl-36 (0.43 barn) still has a total neutron capture cross section of 33.45 barn.

General data

Name of the isotope:Chlorine-35; Cl-35Symbol:³⁵Cl or 3517ClMass number A:35 (= number of nucleons)Atomic number Z:17 (= number of protons)Neutrons N:18Isotopic mass:34.9688527(3) u (atomic weight of Chlorine-35)Nuclide mass:34.959527 u (calculated nuclear mass without electrons)Mass excess:-29.01352 MeVMass defect:0.32014133200001 u (per nucleus)Nuclear binding energy:298.20972991 MeV (per nucleus)
8.520278 MeV (average binding energy per nucleon)Separation energy:S_N = 12.64476(5) MeV (first neutron)
S_P = 6.37081(4) MeV (first proton)Half-life:stableSpin and parity:
(nuclear angular momentum)3/2+Magnetic dipole moment:μ(μ_N) = +0.82170(2)Charge radius:3.3654(191) femtometer fmMirror nucleus:Argon-35Year of discovery:1919

Parent Nuclides

Direct parent isotopes are: ³⁵Ar, ³⁵S, ³⁶K.

Occurrence

Comparison of the natural Chlorine isotopes including isotopic abundance (mole fraction of the isotope mixture in percent):

	Atomic Mass m_a	Quantity	Half-life	Spin
Chlorine Isotopic mixture	35.45 u	100 %
Isotope ³⁶Cl	35.96830682(4) u	[trace]	3.013(15) × 10⁵ a	2+
Isotope ³⁷Cl	36.9659026(4) u	24.2 % [23.9 - 24.5 %]	stable	3/2+
Isotope ³⁵Cl	34.9688527(3) u	75.80(17) % [75.5 - 76.1 %]	stable	3/2+

NMR data

Nuclear magnetic properties of the NMR active Nuclide ³⁵Cl

Isotope:³⁵Cl-NMRQuantity:75.80(17) % [75.5 - 76.1 %]Spin:3/2+Nuclearmagnetic moment
μ/μ_N:+0.82170(2)Gyromagnetic ratio γ:2.624 · 10⁷ rad T^-1 s^-1Nuclear g-factor:g_l = 0.5478Quadrupole moment Q:- 0.08112 barn (100 fm²)Resonance frequency:v₀ = 4.1765 at 1 TFrequency ratio:Ξ(³⁵Cl) = 9.797909 %Relative Sensitivity:0.00472 (H₀ = const.)
0.4905 (v₀ = const.)
[related to ¹H = 1.000]Reference compound:
(conditions)sodium chloride solution with 0.1 M NaCl in deuterium oxide (line width 11.4 Hz).

³⁵Cl, along with ³⁷Cl is one of the two natural chlorine isotopes that are suitable for NMR spectroscopy (³⁶Cl only occurs in trace amounts and is radioactive). ³⁵Cl-NMR spectroscopy is mainly used to investigate ionic and inorganic chlorides. In the spectra of organic chlorine compounds, the nucleus delivers very broad signals that become even broader with decreasing symmetry and the molecular size of the sample, which makes the use of this method in organic chemistry strongly limited.

Compared to the ³⁷Cl nucleus, the ³⁵Cl NMR is significantly more sensitive, but provides somewhat broader signals and shows a slightly worse resolution. The chemical shift range is between -50 and 1050 ppm.

Isotones and Isobars

The following table shows the atomic nuclei that are isotonic (same neutron number N = 18) and isobaric (same nucleon number A = 35) with Chlorine-35. Naturally occurring isotopes are marked in green; light green = naturally occurring radionuclides.

Z	Isotone N = 18	Isobar A = 35
7	²⁵N
8	²⁶O
9	²⁷F
10	²⁸Ne
11	²⁹Na	³⁵Na
12	³⁰Mg	³⁵Mg
13	³¹Al	³⁵Al
14	³²Si	³⁵Si
15	³³P	³⁵P
16	³⁴S	³⁵S
17	³⁵Cl	³⁵Cl
18	³⁶Ar	³⁵Ar
19	³⁷K	³⁵K
20	³⁸Ca	³⁵Ca
21	³⁹Sc
22	⁴⁰Ti
23	⁴¹V
24	⁴²Cr
25	⁴³Mn