Cadmium (Cd)
transition-metalSolid
標準原子量
112.414 u電子配置
[Kr] 5s2 4d10融点
321.07 °C沸点
766.85 °C密度
8690 kg/m³酸化数
−2, +1, +2電気陰性度（Pauling）
1.69第1イオン化エネルギー
8.99382 eV発見年
1817原子半径
155 pm詳細
Cadmium is a soft, bluish-white post-transition metal in group 12. It occurs mainly as a minor constituent of zinc ores and is usually recovered as a by-product of zinc refining. Chemically it is dominated by the +2 oxidation state and forms many salts with ionic character. Its technological importance has declined in some applications because cadmium and many cadmium compounds are highly toxic, but it remains useful where particular electrochemical, pigment, or semiconductor properties are required.
Soft bluish metal belonging to group 12 of the periodic table. Extremely toxic even in low concentrations. Chemically similar to zinc, but lends itself to more complex compounds. Discovered in 1817 by F. Stromeyer.
The name derives from Greek kadmeia for "calamine" (zinc carbonate), with which it was found as an impurity in nature. It may have been found in furnace flue dust in Thebes, a city in the Boeottia region of central Greece. The mythological king of Phoenicia, Cadmus, founded Thebes and would be a source for the name of the ore. The element was discovered and first isolated by German physician Friedrich Stromeyer in 1817.
Cadmium was discovered by Friedrich Strohmeyer, a German chemist, in 1817 while studying samples of calamine (ZnCO3). When heated, Strohmeyer noticed that some samples of calamine glowed with a yellow color while other samples did not. After further examination, he determined that the calamine that changed color when heated contained trace amounts of a new element. There is only one mineral that contains significant amounts of cadmium, greenockite (CdS), but it is not common enough to mine profitably. Fortunately, small amounts of cadmium are found in zinc ores and most of the cadmium produced today is obtained as a byproduct of mining and refining zinc.
From the Latin word cadmia, Greek kadmeia - the ancient name for calamine, zinc carbonate. Discovered by Stromeyer in 1817 from an impurity in zinc carbonate. Cadmium most often occurs in small quantities associated with zinc ores, such as sphalerite (ZnS). Greenockite (CdS) is the only mineral of any consequence bearing cadmium. Almost all cadmium is obtained as a by-product in the treatment of zinc, copper, and lead ores. It is a soft, bluish-white metal which is easily cut with a knife. It is similar in many respects to zinc. In 1927 the International Conference on Weights and Measures redefined the meter in terms of the wavelength of the red cadmium spectral line (i.e. 1m = 1.553,164.13 wavelengths). This definition has been changed (see Krypton).
Pure cadmium is a silvery to bluish-white metal with a bright metallic luster when freshly cut. It is soft, malleable, and relatively low-melting for a structural metal. On exposure to air it slowly develops a dull surface film rather than remaining mirror-bright.
Cadmium metal has been used for corrosion-resistant electroplating on steel, especially where coatings must remain reliable in marine or aerospace service. Nickel-cadmium batteries use cadmium as the negative-electrode active material and remain important in some industrial and emergency applications, although many consumer uses have been replaced. Cadmium compounds are used in selected red, orange, and yellow pigments, in some plastics stabilizers of historical importance, and in cadmium telluride photovoltaic cells. Cadmium is also an efficient neutron absorber in control rods and shielding components.
Cadmium is a poisonous metal and its use is somewhat limited for this reason. Like zinc, cadmium can be electroplated to other materials to protect them from corrosion. Cadmium easily absorbs neutrons and is used to make control rods for nuclear reactors. Cadmium is also used in rechargeable nickel-cadmium batteries.
Cadmium is alloyed with silver to form solder, a metal with a relatively low melting point used to join electrical components, pipes and other metallic items. Cadmium based solders must be handled with care to prevent cadmium poisoning. Cadmium alloys are also used to make low friction bearings that are highly resistant to fatigue.
Hydrated cadmium sulfate (3CdSO4·5H2O), one of cadmium's compounds, is used in a device called a Weston cell, a type of battery that produces a precise voltage used to calibrate medical and laboratory equipment. Cadmium sulfide (CdS), another cadmium compound, is a yellow powder that is used as a pigment. Other cadmium compounds are used in the phosphors of black and white television sets and in the blue and green phosphors in color television sets.
Cadmium is a component of some of the lowest melting alloys; it is used in bearing alloys with low coefficients of friction and great resistance to fatigue; it is used extensively in electroplating, which accounts for about 60% of its use. It is also used in many types of solder, for standard E.M.F. cells, for Ni-Cd batteries, and as a barrier to control nuclear fission. Cadmium compounds are used in black and white television phosphors and in blue and green phosphors for color TV tubes. It forms a number of salts, of which the sulfate is most common; the sulfide is used as a yellow pigment. Cadmium and solutions of its compounds are toxic.
Isotopes in Biology
Metal accumulation is a threat to our world’s water systems and wildlife. As a way to measure the influence of heavy metals on wildlife utilizing mass spectrometric techniques, some researchers use animal food enriched in specific cadmium isotopes. These experiments work by exposing the animals to a diet enriched in 106Cd and/or other stable isotopes of metals (for example, 65Cu and/or 62Ni) for a period of time. Depending on the purpose of the experiment, the residence time of the food in the gut is determined and isotopic compositions of the gut and/or feces are measured viainductively coupled plasma mass spectrometry (ICP-MS). This information is used to measure bio-uptake (absorption and incorporation of a substance by living tissue) and accumulation rates of metals in an exposed animal [355] M. N. Croteau, S. N. Luoma, B. Pellet. Aquat. Toxicol.83, 116 (2007)., [356] M. N. Croteau, S. N. Luoma. Environ. Sci. Technol.43, 4915 (2009)..
Isotopes in Earth/Planetary Science
Molecules, atoms, and ions of the stable isotopes of cadmium possess slightly different physical and chemical properties, and they commonly will be fractionated during physical, chemical, and biological processes, giving rise to variations in isotopic abundances and in atomic weights. There are small but measureable variations in the isotopic abundances of dissolved cadmium in ocean water, which are a consequence of isotopic fractionation associated with biological uptake (Fig. IUPAC.48.1) [357] F. Lacan, R. Francois, Y. Ji, R. M. Sherrell. Geochim. Cosmochim. Acta70, 5104 (2006)., [358] W. Abouchami, S. J. G. Galer, H. J. W. d. Baar, A. C. Alderkamp, R. Middag, P. Laan, H. Feldmann, M. O. Andreae. Earth. Planet. Sci. Lett.305, 83 (2011)., [359] Z. Xue, M. Rehkämper, T. J. Horner, W. Abouchami, R. Middag, T. v. d. Flierd, H. J. W. d. Baar. Earth. Planet. Sci. Lett.382, 161 (2013)..
Isotopes Used as a Source of Radioactive Isotope(s)
112Cd is used to produce the diagnostic radioisotope 111In (with a half-life of 2.8 days) via the reaction 112Cd (p, 2n) 111In [94] International Atomic Energy Agency. Cyclotron Produced Radionuclides: Physical Characteristics and Production Methods, Technical Reports Series No. 468. International Atomic Energy Agency Vienna (2009)..
Cadmium chemistry is centered on Cd²⁺; the +1 state is uncommon and usually involves metal-metal bonded species rather than simple stable salts. Cadmium sulfide, CdS, is a yellow semiconductor and pigment, while cadmium selenide, CdSe, and cadmium telluride, CdTe, are important semiconducting materials. Cadmium oxide, CdO, is a brown to black oxide used in some electronic and plating-related applications. Soluble salts such as cadmium chloride, CdCl₂, and cadmium nitrate, Cd(NO₃)₂, are important laboratory or industrial intermediates but are especially hazardous because they make Cd²⁺ readily bioavailable.
See more information at the Cadmium compound page.
Cadmium metal dust, fumes, and soluble cadmium salts are highly toxic. Inhalation of cadmium oxide, CdO, fumes from heating or welding cadmium-containing materials can cause severe acute lung injury. Chronic exposure can damage kidneys and bones, and cadmium compounds are recognized human carcinogens in occupational settings. Cadmium has no known essential biological role, and exposure control is central to its handling.
Failure to appreciate the toxic properties of cadmium may cause workers to be unwittingly exposed to dangerous fumes. Silver solder, for example, which contains cadmium, should be handled with care. Serious toxicity problems have been found from long-term exposure and work with cadmium plating baths. Exposure to cadmium dust should not exceed 0.01 mg/m3 (8-hour time-weighted average, 40-hour week). The ceiling concentration (maximum), for a period of 15 min, should not exceed 0.14 mg/m3. Cadmium oxide fume exposure (8-hour, 40-hour week) should not exceed 0.05 mg/m3, and the maximum concentration should not exceed 0.05 mg/m3. These values are presently being restudied and recommendations have been made to reduce the exposure.
Cadmium is a naturally occurring trace element released by weathering, volcanism, and the processing or combustion of mineral materials. It is relatively mobile under acidic conditions and can accumulate in soils and sediments. Plants can take up Cd²⁺ from contaminated soil, allowing entry into food chains, especially near smelters, phosphate fertilizers, or waste sites. In aquatic systems, sulfide-rich sediments can immobilize cadmium as poorly soluble sulfides.
Cadmium supply is tied closely to zinc production because most recoverable cadmium is obtained from flue dusts, residues, and electrolytic refining streams during zinc processing. Demand has contracted in many regions as restrictions and substitution reduced uses in pigments, stabilizers, and consumer batteries. Remaining demand is concentrated in industrial nickel-cadmium batteries, specialized coatings, semiconductors, and control materials. Recycling is important for batteries and some industrial scrap, both to recover material and to keep cadmium out of general waste streams. There is no large independent cadmium mining industry comparable to major base metals.
Obtained as a by product of zinc refining.
Cadmium is a relatively rare element in the cosmos. Its stable isotopes are produced mainly by slow and rapid neutron-capture processes in earlier generations of stars, followed by dispersal into interstellar material. In planets it behaves as a chalcophile and moderately volatile element, so it tends to associate with sulfide phases and can be depleted from high-temperature condensed materials.
- Cadmium was identified in the early 19th century as an impurity in zinc compounds.
- Cadmium plating offers good sacrificial protection but is now tightly restricted in many applications.
- Cadmium yellow pigment is based largely on cadmium sulfide, CdS.
- Natural cadmium consists of several stable isotopes and a few very long-lived radioisotopes.
- Cadmium can form low-melting alloys used in some fusible safety devices.
- Rice and leafy vegetables can be significant dietary cadmium sources in contaminated areas.
画像
性質
物理的性質
- 原子半径（経験値）
- 155 pm 全元素の原子半径（経験値）を比較 →
- 共有結合半径
- 144 pm 全元素の共有結合半径を比較 →
- ファンデルワールス半径
- 158 pm 全元素のファンデルワールス半径を比較 →
- 金属半径
- 138 pm 全元素の金属半径を比較 →
- 密度
- 8690 kg/m³ 全元素の密度を比較 →
- モル体積
- 0.0131 L/mol
- 標準温度・圧力（STP）での相
- 固体 全元素の標準温度・圧力（STP）での相を比較 →
- 融点
- 321.07 °C 全元素の融点を比較 →
- 沸点
- 766.85 °C 全元素の沸点を比較 →
- 熱伝導率
- 96.9 W/(m·K) 全元素の熱伝導率を比較 →
- 比熱容量
- 0.232 J/(g·K) 全元素の比熱容量を比較 →
- モル熱容量
- 26.02 J/(mol·K) 全元素のモル熱容量を比較 →
- 結晶構造
- 六方最密充填構造 全元素の結晶構造を比較 →
化学的性質
- 電気陰性度（Pauling）
- 1.69 全元素の電気陰性度（Pauling）を比較 →
- 電気陰性度（Allen）
- 1.52
- 電子親和力
- -0.7 eV (負の値—この原子は電子を取り込まないと予測される)
- 第1イオン化エネルギー
- 8.99382 eV 全元素の第1イオン化エネルギーを比較 →
- 第2イオン化エネルギー
- 16.908371 eV 全元素の第2イオン化エネルギーを比較 →
- 第3イオン化エネルギー
- 37.468129 eV 全元素の第3イオン化エネルギーを比較 →
- 第4イオン化エネルギー
- 51.000176 eV 全元素の第4イオン化エネルギーを比較 →
- 第5イオン化エネルギー
- 67.900234 eV 全元素の第5イオン化エネルギーを比較 →
- 酸化数
- −2, +1, +2 全元素の酸化数を比較 →
- 価電子
- 12 全元素の価電子を比較 →
- 電子配置
- [Kr] 5s2 4d10
熱力学的性質
- 融解熱
- 0.06436234 eV 全元素の融解熱を比較 →
- 蒸発熱
- 1.036431 eV 全元素の蒸発熱を比較 →
- 昇華熱
- 1.160802 eV
- 原子化熱
- 1.160802 eV
- 原子化エンタルピー
- 1.158729 eV
原子核
- 陽子数
- 48 全元素の陽子数を比較 →
- 中性子数
- 64 全元素の中性子数を比較 →
- 既知の同位体
- 42 全元素の既知の同位体を比較 →
- 安定同位体
- 3 全元素の安定同位体を比較 →
- 最も安定な同位体
- Cd-112
- 発見年
- 1817
存在度
- 存在度（地殻）
- 0.15 mg/kg 全元素の存在度（地殻）を比較 →
- 存在度（海洋）
- 1.1 × 10−4 mg/L 全元素の存在度（海洋）を比較 →
結晶構造
- 格子定数a
- 298 pm
電子構造
- 各電子殻の電子数
- 2, 8, 18, 18, 2 全元素の各電子殻の電子数を比較 →
識別子
- CAS登録番号
- 7440-43-9 全元素のCAS登録番号を比較 →
- 項記号
- 1S0
- InChI
- InChI=1S/Cd
- InChI Key
- BDOSMKKIYDKNTQ-UHFFFAOYSA-N
電子配置 測定値
Cd: 4d¹⁰ 5s²[Kr] 4d¹⁰ 5s²1s² 2s² 2p⁶ 3s² 3p⁶ 3d¹⁰ 4s² 4p⁶ 4d¹⁰ 5s²原子モデル
同位体によって中性子数、質量、安定性は変わりますが、中性原子の電子配置は変わりません。
模式的な原子モデルです。実際の縮尺とは異なります。
原子の指紋
発光／吸収スペクトル
同位体分布
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 |
|---|---|---|---|
| 110 安定 | 109.90300661 ± 0.00000061 | 12.4900% | 安定 |
| 111 安定 | 110.90418287 ± 0.00000061 | 12.8000% | 安定 |
| 112 安定 | 111.90276287 ± 0.0000006 | 24.1300% | 安定 |
相／状態
理由: 融点（321.07 °C）より296.1 °C低い
模式図、実際の縮尺とは異なります
相転移点
相転移エネルギー
融点で1 molを融解させるのに必要なエネルギー
沸点で1 molを蒸発させるのに必要なエネルギー
昇華点で1 molを昇華させるのに必要なエネルギー
密度
標準条件下
標準条件下
原子スペクトル
全48件中10件を表示しています。 イオンの電荷の昇順で並べています。
スペクトル線データの収録状況 ?
| イオン | 電荷 | スペクトル線の総数 | 遷移確率 | 準位の表記 |
|---|---|---|---|---|
| Cd I | 0 | 69 | 18 | 69 |
| Cd II | +1 | 173 | 87 | 173 |
| Cd III | +2 | 95 | 0 | 0 |
| Cd IV | +3 | 102 | 0 | 0 |
準位データの収録状況 ?
| イオン | 電荷 | 準位 |
|---|---|---|
| Cd I | 0 | 128 |
| Cd II | +1 | 101 |
| Cd III | +2 | 48 |
| Cd IV | +3 | 52 |
| Cd V | +4 | 2 |
| Cd VI | +5 | 2 |
| Cd VII | +6 | 2 |
| Cd VIII | +7 | 2 |
| Cd IX | +8 | 2 |
| Cd X | +9 | 2 |
イオン半径
| 電荷 | 配位 | スピン | 半径 |
|---|---|---|---|
| +2 | 4 | データなし | 78 pm |
| +2 | 5 | データなし | 87 pm |
| +2 | 6 | データなし | 95 pm |
| +2 | 7 | データなし | 103 pm |
| +2 | 8 | データなし | 110.00000000000001 pm |
| +2 | 12 | データなし | 131 pm |
化合物
同位体 (3)
| 質量数 | 原子質量（u） | 天然存在比 | 半減期 | 崩壊形式 | |
|---|---|---|---|---|---|
| 110 安定 | 109.90300661 ± 0.00000061 | 12.4900% ± 0.1800% | 安定 | stable | |
| 111 安定 | 110.90418287 ± 0.00000061 | 12.8000% ± 0.1200% | 安定 | stable | |
| 112 安定 | 111.90276287 ± 0.0000006 | 24.1300% ± 0.2100% | 安定 | stable |
スペクトル線
| 波長（nm） | 強度 | 電離段階 | 種類 | 遷移 | 精度 | 出典 | |
|---|---|---|---|---|---|---|---|
| 398.19257 nm | 10 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.9s 1S | 測定値 | NIST | |
| 414.03021 nm | データなし | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.7d 1D | 測定値 | NIST | |
| 430.66718 nm | 8 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.8s 1S | 測定値 | NIST | |
| 441.29894 nm | 3 | Cd I | emission | 4d10.5s.5p 3P* → 4d10.5s.6s 1S | 測定値 | NIST | |
| 466.2352 nm | 8 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.6d 1D | 測定値 | NIST | |
| 467.815 nm | 200 | Cd I | emission | 4d10.5s.5p 3P* → 4d10.5s.6s 3S | 測定値 | NIST | |
| 479.99121 nm | 300 | Cd I | emission | 4d10.5s.5p 3P* → 4d10.5s.6s 3S | 測定値 | NIST | |
| 508.58214 nm | データなし | Cd I | emission | 4d10.5s.5p 3P* → 4d10.5s.6s 3S | 測定値 | NIST | |
| 515.46618 nm | 6 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.7s 1S | 測定値 | NIST | |
| 609.9142 nm | 300 | Cd I | emission | 4d10.5s.6s 3S → 4d10.5s.8p 3P* | 測定値 | NIST | |
| 611.1495 nm | 100 | Cd I | emission | 4d10.5s.6s 3S → 4d10.5s.8p 3P* | 測定値 | NIST | |
| 632.51689 nm | 100 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.5d 3D | 測定値 | NIST | |
| 633.00149 nm | 30 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.5d 3D | 測定値 | NIST | |
| 643.84695 nm | 2000 | Cd I | emission | 4d10.5s.5p 1P* → 4d10.5s.5d 1D | 測定値 | NIST | |
| 677.8116 nm | 30 | Cd I | emission | 4d10.5s.6s 1S → 4d10.5s.8p 1P* | 測定値 | NIST | |
| 734.5665 nm | 1000 | Cd I | emission | 4d10.5s.6s 3S → 4d10.5s.7p 3P* | 測定値 | NIST |
詳細な性質
共有結合半径（詳細）
- 共有結合半径（Pyykkö）
- 136 pm
- 共有結合半径（Pyykkö、二重結合）
- 144 pm
- 共有結合半径（Bragg）
- 160 pm
ファンデルワールス半径
- Batsanov
- 220 pm
- Alvarez
- 249 pm
- UFF
- 284.8 pm
- MM3
- 250 pm
原子半径と金属半径
- 原子半径（Rahm）
- 238 pm
- 金属半径（C12）
- 151 pm
番号付けの尺度
- Mendeleev
- 78
- Pettifor
- 75
- Glawe
- 75
電気陰性度の尺度
- Ghosh
- 0
- Miedema
- 4
- Gunnarsson–Lundqvist
- 4
- Robles–Bartolotti
- 3
分極率と分散
- 双極子分極率
- 46 a.u.
- 双極子分極率（不確かさ）
- 2 a.u.
- C₆ (Gould–Bučko)
- 405 Ha·Bohr6
ミーデマパラメータ
- ミーデマモル体積
- 13 cm3/mol
- ミーデマ電子密度
- 2
供給リスクと経済性
- 生産集中度
- 32
- 相対供給リスク
- 7
- 埋蔵量の分布
- 20
- 政治的安定性（最大生産国）
- 24
- 政治的安定性（最大埋蔵国）
- 11
相転移と同素体
| 融点 | 594.22 K |
| 沸点 | 1040.15 K |
酸化数の分類
専門参考データ
遮蔽定数 (10)
| n | 軌道 | σ |
|---|---|---|
| 1 | s | 0.9744 |
| 2 | p | 4.091 |
| 2 | s | 12.6142 |
| 3 | d | 14.3931 |
| 3 | p | 17.3085 |
| 3 | s | 17.1588 |
| 4 | d | 32.1232 |
| 4 | p | 28.5888 |
| 4 | s | 27.1308 |
| 5 | s | 39.808 |
結晶半径の詳細 (6)
| 電荷 | CN | スピン | rcrystal (pm) | 由来 |
|---|---|---|---|---|
| 2 | IV | 92 | ||
| 2 | V | 101 | ||
| 2 | VI | 109 | ||
| 2 | VII | 117 | calculated, | |
| 2 | VIII | 124 | calculated, | |
| 2 | XII | 145 |
同位体の崩壊形式 (59)
| 同位体 | モード | 強度 |
|---|---|---|
| 94 | B+ | — |
| 94 | B+p | — |
| 95 | B+ | 100% |
| 95 | B+p | 4.6% |
| 96 | B+ | 100% |
| 96 | B+p | 1.6% |
| 97 | B+ | 100% |
| 97 | B+p | 7.4% |
| 98 | B+ | 100% |
| 98 | B+p | 0% |
X線散乱因子 (510)
| エネルギー (eV) | f₁ | f₂ |
|---|---|---|
| 10 | — | 0.40004 |
| 10.1617 | — | 0.41842 |
| 10.3261 | — | 0.43764 |
| 10.4931 | — | 0.45775 |
| 10.6628 | — | 0.49362 |
| 10.8353 | — | 0.53685 |
| 11.0106 | — | 0.59258 |
| 11.1886 | — | 0.66328 |
| 11.3696 | — | 0.74242 |
| 11.5535 | — | 0.86125 |
追加データ
Estimated Crustal Abundance
The estimated element abundance in the earth's crust.
1.5×10-1 milligrams per kilogram
参考文献 (1)
Estimated Oceanic Abundance
The estimated element abundance in the earth's oceans.
1.1×10-4 milligrams per liter
参考文献 (1)
参考文献
(9)
Data deposited in or computed by PubChem
The half-life and atomic mass data was provided by the Atomic Mass Data Center at the International Atomic Energy Agency.
Element data are cited from the Atomic weights of the elements (an IUPAC Technical Report). The IUPAC periodic table of elements can be found at https://iupac.org/what-we-do/periodic-table-of-elements/. Additional information can be found within IUPAC publication doi:10.1515/pac-2015-0703 Copyright © 2020 International Union of Pure and Applied Chemistry.
The information are cited from Pure Appl. Chem. 2018; 90(12): 1833-2092, https://doi.org/10.1515/pac-2015-0703.
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The periodic table at the LANL (Los Alamos National Laboratory) contains basic element information together with the history, source, properties, use, handling and more. The provenance data may be found from the link under the source name.
The periodic table contains NIST's critically-evaluated data on atomic properties of the elements. The provenance data that include data for atomic spectroscopy, X-ray and gamma ray, radiation dosimetry, nuclear physics, and condensed matter physics may be found from the link under the source name. Ref: https://www.nist.gov/pml/atomic-spectra-database
This section provides all form of data related to element Cadmium.
The element property data was retrieved from publications.