Everybody help me to ask a question about chemistry concepts

An ionic compound is a chemical bond formed by an atom completely giving the outermost electron to another one.

A covalent compound is a chemical bond formed by two or more atoms sharing electron pairs.

Ionic bonds are more important than covalent bonds, and both of them are ionic compounds, and there are other problems to be solved, which are slowly discovered).

Atomic crystals have a high melting boiling point and a high density of SiO2 si diamond These just keep in mind.

Molecular crystals are mostly covalent compounds Ionic crystals are mostly ionic compounds.

The melting boiling point is the highest for atomic crystals, and then for ionic crystals, and for molecular crystals, it is relatively low.

You can highlight the key points and remember a representative object each, such as:

Ionic compound NaCl, covalent molecule O2, covalent compound H2O, atomic crystal Si, molecular crystal SiO2, ionic crystal NaCl

Buy a reference book, and the ones on it are very detailed.

Even if someone finds it out for you, it's pretty much the same as that, and you don't necessarily have the patience to look at it.

1: This question is based on the conservation of electron transfer, because the acid is sufficient, and the metal directly added is 1mol).

A 3mol l HCl (both metals react, electrons transfer (2+3) 1mol, to form hydrogen.

b 3mol l hno3 (nitric acid will not react with metal to form hydrogen) c 8mol l NaOH (only aluminum reacts with electron transfer of 31mol to form hydrogen D H2SO4 (aluminum passivates when it is not heated, sulfur dioxide is generated when it is heated, and crystals are precipitated.) Precipitated is NaHCO3.

3.I don't know 0 0

Urea con2H4 (relative molecular mass 60).

2. Hydrogen element, sulfur element.

Hydrogen atoms, sulfur atoms.

Hydrogen 1, sulfur 32 (stands for relative atomic mass, which is a very old saying for the Pybi) 3, seven periods of seven main space-track groups.

4. What are the properties of the elements?

1. Zn can replace Fe, but Cu cannot replace Fe. It can be stated that the order is zn fe cu, so it is feasible.

2. FE is not involved, and the order of FE cannot be judged. Not feasible.

3. Zn can replace Fe and Cu, which can only indicate that Zn is the most active, but it cannot judge the order of Fe and Cu. Not feasible.

4. Fe can replace Cu, but not Zn. It can be stated that the order is zn fe cu, which is feasible.

Select A

1. Zinc can react with ferrous ions, and copper does not react with ferrous ions, which can be judged.

4. It can react with iron and copper ions, but not with zinc ions, and it can be judged to choose A

At the moment, I can only tell you that I choose A), as for why I can't say well.

That liquid is a solution of baking soda (sodium bicarbonate: naHCO3), put the paper in the dish, because of the capillary phenomenon, the paper absorbs the baking soda to the full, and the whole tree is full of baking soda, after a while, the water on the tree dries up (is evaporated), then the sodium bicarbonate in the solution is precipitated in the form of crystals, because the solubility of naHCO3 is larger, and more crystals are precipitated after the water dries, forming something like snow on the tree. This is the same principle as evaporating solvents to produce crystals.

I've never seen anything on the first floor.

On the second floor, the mercury oxidizes to produce a red liquid! Please, ah, ah, there's a chemical equation to prove it: hg

o2== (Condition: Heating) Hgo2, you can go to the encyclopedia to check whether mercury oxide (Hgo2) is red.

1.Chemical change to form a new substance, there must be a new chemical bond formation, but due to the different forms of reactants, there may be no break of the old bond, for example, you said that barium chloride and sodium sulfate both exist in ionic form in aqueous solution, and there is no break of the old bond when barium sulfate is formed. However, for many chemical reactions, such as magnesium burning in the air to form magnesium oxide, there are both old bond breaks and new bonds are formed in the process.

The element is chromium, and the outermost 6 electrons you are talking about are its valence electrons, and it can lose one, three, or six electrons, which is a valence element, and it depends on the situation.

1.Just like you gave the example that the reaction was preceded by ionic bonds, and after the reaction, ionic bonds were formed.

The element is chromium and his electron configuration is 2,8,13,1, which is related to his electron sublayer. Chromium loses 3 electrons and is more stable.

1. This is not clear、、、 because the question is too absolute, it should be wrong.

2. CR belongs to the subgroup of elements, the schematic diagram of the atomic structure of the extranuclear electron arrangement of the subgroup element is not as you imagine that the inner electrons are full to exclude the outer electrons, and the correct arrangement of the extranuclear electrons of the 24th element chromium should be 2 8 13 1, but its valency cannot be determined because of this, and the valency is generally a 、、、 to remember