第一章单元测试
Trace elements are essential to life.
Elements with similar chemical properties generally fall into the same group in the periodic table.
A pure substance always has the same physical and chemical properties and is either an element or a compound.
Calcium oxide is an inorganic compounds.
Any chemical species capable of binding to electron pairs is called a Lewis acid; any molecule that tends to donate an electron pair is referred to as a Lewis base.
In either case, the position of the multiple bond is indicated by numbering from the end of the chain, starting at the end that will assign the lower number to the first carbon atom of the multiple bond.
Ethers tend to be reactive, and low molecular mass ethers are often used as solvents.
If one or both of the hydrogen atoms on the amide nitrogen atom are replaced by hydrocarbon groups, the structure is named as an N-substituted amide.
By doing research in chemistry, we can find new cures for diseases as well as better chemicals to use in our natural environment.
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答案:对
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答案:对
