Secondly, kiwifruit contains arsenic. Theoretically, the compound of pentavalent arsenic is harmless to human body, but if it is eaten together with kiwi fruit rich in vitamin C, pentavalent arsenic meets vitamin C, which turns pentavalent arsenic into trivalent arsenic containing highly toxic arsenic. If it is used together for a long time, with the accumulation of poisons, toxic symptoms such as nausea can be seen.
Therefore, don't eat a kiwi fruit after eating crabs.
Note: I am also a chemistry teacher. Let's review: arsenic.
Arsenic, commonly known As polonium, is a metalloid element, which is located in the 4th period and the VA family in the periodic table of chemical elements, with the proton number of 33 and the element symbol as. Simple substance exists in the form of three allotropes: gray arsenic, black arsenic and yellow arsenic. Arsenic exists widely in nature, and hundreds of arsenic minerals have been discovered. Arsenic and its compounds are used in pesticides, herbicides, insecticides and many kinds of alloys. Its compound arsenic trioxide is called arsenic, which is a very toxic substance.
The three allotropes of elemental arsenic are gray arsenic, yellow arsenic and black arsenic, among which gray arsenic is the most common.
Gray arsenic is a double-layer structure composed of many interlocking six-member rings. Because the bonding force between layers is weak, it is brittle and hard, with metallic luster and easy to be pounded into powder. Amorphous gray arsenic is a semiconductor with a band gap of 1.2- 1.4 eV.
Yellow arsenic is soft and waxy, which is similar to white phosphorus to some extent. The molecular structures of yellow arsenic and white phosphorus are tetrahedral structures composed of four atoms connected with each other by a single bond. This kind of unstable allotrope in the form of molecular crystal is the most volatile, the lowest density and the most toxic solid. Yellow arsenic solid is produced by rapidly cooling arsenic vapor, which is quickly transformed into gray arsenic under illumination. The density of yellow arsenic is 1970kg/m? . The structure of black arsenic is similar to that of red phosphorus.
Elemental arsenic has a melting point of 8 17℃(28 atm). When it is heated to 6 13℃, it can be sublimated directly into vapor without liquid state, and arsenic vapor has an unpleasant smell of garlic. The valence of arsenic is -3, +3 and +5. The first ionization energy is 9.8 1 electron volt. If arsenic vapor is crystallized above 360℃, hexagonal α -arsenic (gray arsenic, density 5720kg/m3) can be obtained. Glassy β-arsenic (black arsenic, density 4730 kg/m3) is obtained by vapor deposition below 300℃. Quenching arsenic vapor can obtain square crystal γ arsenic (yellow arsenic, density 2030 kg/m3). γ -arsenic is soluble in carbon disulfide.