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Group VIII of the periodic table includes iron (Fe), cobalt (Co), nickel (Ni), ruthenium (Ru), rhodium (Rh), palladium (Pd), starvation (Os), iridium (Ir), platinum ( Pt) A total of 9 elements
.
Usually the first three elements are called iron-based elements, and the last six elements are called platinum-based elements
.
The valence electron configuration of iron-based elements is (n-1)d 6~8 ns ²
.
In addition to the two s electrons participating in the bonding, the inner d orbital electrons may also participate in the bonding.
Therefore, iron-based elements have other oxidation states besides the stable +2 oxidation state
Iron minerals mainly include hematite Fe 2 O 3 , magnetite Fe 3 O 4 , limonite 2Fe 2 O 3 ·3H 2 O, and siderite FeCO 3
.
It is cobalt arsenide mineral ore and sulfide minerals, such as arsenic, cobalt ore CoAs in 2 , cobaltite CoAsS sulfur and cobalt ore of Co 2 S .
4 and the like
Among the platinum group elements, only Os (5d 6 s 2 ) and Ir (5d 9 6s 2 ) electrons are normally arranged, and the electrons of the other 4 elements are all specially arranged: Ru 4d 7 5s 1 , Rh 4d 5 s 1 , Pd 4d 10 5s 0 , Pt5d 9 6s 1 , the outermost s orbitals are reduced by 1 or 2 electrons, and they are arranged on the second outer d orbitals
.
The inner d orbitals of platinum group elements have stronger ability to participate in bonding and show more oxidation states
.
Elemental elements of iron series
Iron has played an irreplaceable role in the development of human society
.
Around 1400 BC, human society began to enter the "Iron Age".
The use of iron tools made it possible to reclaim and cultivate a large area of farmland, significantly increase social productivity, and promote human beings from primitive society into slave society
The iron elements are silver-white and shiny metals with strong magnetism.
Many iron, cobalt, and nickel alloys are good magnetic materials
.
Iron and nickel are ductile, cobalt is hard and brittle, and low-purity cast iron is also brittle
.
Iron-based metals have good resistance to strong alkalis, and platinum-based metals have strong acid resistance
.
Metal nickel, palladium, and platinum all have the ability to absorb hydrogen.
Among them, metal has the strongest ability to absorb hydrogen.
The reactivity of iron, cobalt, and nickel decreases, and all of them can react with dilute acid to replace hydrogen
.
Lump iron, cobalt, and nickel are stable in air and pure water, and iron with impurities will slowly rust in humid air to form a brown rust Fe 2 O 3 ·nH 2 O with a loose structure
.
The iron surface treated with concentrated nitric acid or concentrated sulfuric acid can form a dense oxide film, which can protect the iron surface from the erosion of moist air
.
Cobalt and nickel are oxidized by air to form a thin and dense film, which protects the metal from further erosion
.
Iron elements are difficult to react with strong bases
.
Among them, nickel has the highest stability against alkalis, and nickel crucibles can be used to melt strong alkalis
.
Iron is less reactive with a nonmetallic substance at normal temperature, but in the case of red hot, sulfur, chlorine, bromine and other violent action occurs
.
The smelting of cobalt and nickel first converts minerals into oxides, and then reduces the oxides with carbon to obtain low-purity metals
.
High-purity metals can be obtained by electrolysis
.