Chemistry masters, please enter you can finish the third year of junior high school .

1. The electron shell increases sequentially from top to bottom, and the law of increase should be remembered by yourself; From left to right, the number of electrons in the outermost electron shell increases sequentially; The main element requires memorization in high school, and it rhymes with memorization, so as long as you master the law of change of atomic number and strengthen memory on the basis of understanding, you can achieve the goal.

2. The change of the main group elements is as mentioned above, and the law of the secondary group is not obvious, and it is usually not required, and the noble gas is the outermost electron of 8 (helium is 2), which is not easy to lose and get electrons, very stable, also known as noble gas.

3. To learn chemistry well, it mainly depends on exercises to strengthen training (personal understanding is so).

1.Press 1h2he3li ......Slip it on.

2.The valence of the same column of elements is the same, and the last column is the column of noble gases, which do not have many reserves in life, and they are all gaseous at long temperatures. They are stable in nature and do not react easily with other substances.

3.The relative atomic mass of an element is about twice its atomic number, sometimes with small fluctuations.

4.Chemistry in junior high school is relatively simple, as long as you understand and can use what you have learned to write chemical equations according to the topic prompts.

5.In my experience, I think that good English is still related to chemistry, and students with good English still have a little advantage in learning chemistry.

1.In junior high school, you only need to memorize the element period to 20, and in high school, you only need to memorize to 36, so I think hard memorization is fine. As for the rules, you will learn them in high school, which is a bit complicated, so it is better not to study high school things if you are so nervous in the third year of junior high school.

2 "main group" does not have d and f energy levels, the secondary group has, the rare gas is very stable, and the outermost 8 electrons are also high school knowledge

3. Any subject can be learned well as long as you are interested in it, and you should pay attention to chemical equations I am not very good at English, and I also study chemistry, and I can also Chemistry is a liberal arts in science, and chemistry with a good liberal arts should be good

As long as you memorize the first twenty in the third year of the periodic table, almost just rote memorization, the teacher didn't say that there is any rule, but I am also very familiar with it, I have a full score in physics and chemistry in the middle school entrance examination this year, it is very simple, the teacher will teach you, the main family, the secondary family can not be used in the third year of junior high school, noble gases are elements with a very stable atomic structure, the teacher will say which ones to memorize, junior high school chemistry is just an introduction, all questions are considered with the simplest ideas (except for competitions), junior high school chemistry to learn well, only remember the knowledge points, It's almost the same as English, you have to memorize a lot of things, probably because of this, good English chemistry is also very good.

1.I remember that in junior high school, I only need to memorize the first 20 9s.

2.The main family is the one with what a is written on the top, and the subfamily is written with what b, and the rare gas is a very rare gas Very stable, it is the 0 family (the rightmost column).

3.Chemistry. Memorize.

When you are in high school, the teacher will want you to explain why many phenomena are the way they are, so when the time comes, you will understand 8, and now you can only memorize them.

The first 20 elements on the back are fine, and the latter ones don't need to be memorized by each!

Answer: (1) The egg floats on the surface of the water.

Because the density of saturated salt water is greater than the density of eggs, the volume of eggs remains unchanged, f float = liquid density g v row Therefore, when salt powder is gradually added to the glass until the solution is saturated, the liquid density becomes larger, and the buoyancy of the egg becomes larger, and when it is greater than the gravity of the egg, the egg floats up and floats on the water.

2) There will be a lot of bubbles on the surface of the egg. The eggs float up and down in the glass.

The chemical equation is: CaCO3 + 2HCl ==CaCl2 + H2O + CO2 (the main component of egg shell is CaCO3).

1.If salt powder is gradually added to the glass until the solution is saturated (the density of saturated salt water is greater than that of salt water), the phenomenon that will be observed is that the egg rises because the buoyancy force on the egg is greater than the gravitational force

2.If concentrated hydrochloric acid is gradually added to the glass, bubbles will appear on the surface of the eggshell. This will make the egg move up and down in the cup, writing the chemical equation that occurs in the above process CaCO3+2HCl=CaCl2+H2O+CO2

1. Egg floats (egg density is less than concentrated brine density).

2. Bubbles (carbon dioxide) appear on the surface of the egg shell and move up and down (shaking).

Equation 2: CaCO3 + 2HCl = CO2 (up arrow) + H2O + CACl2

m(na)>m(na+)

r(cl) is too long, almost forgotten, na+ is to lose an ion, cl- is to gain an ion, the mass should be greater than the loss!

On the right side of the MC2H5OH+23O2---2CO+14CO2+NH2O equation, there are 16 C's, so we can know that M=8, so there are 48Hs on the left side of the Fang Zhimin program, so N=24

I forgot about the junior high school method, which is easier to solve with the Fangsun Zaoming method in the high rule, because in the mixture of co:CO2=1:, the mass of C is 12g, and the mass of O is 30g.

So the mass of C in CO is, i.e., CO, CO2

Therefore, it can be seen that the amount of substances that consume ethanol is 23g

Mixture: beer, air, lime water, natural gas (the main component is methane, and a small amount of ethane, propane and butane, in addition to hydrogen sulfide, carbon dioxide, nitrogen and water vapor and trace amounts of inert gases, such as helium and argon, etc.), iodine wine, dilute sulfuric acid.

Compounds: Limestone, Sodium Carbonate, Ethanol (Organic Compounds), Manganese Dioxide, Dry Ice Oxide: Ice-Water Mixture, Dry Ice.

Non-metallic elements: liquid oxygen, sulfur powder.

Mixture: dilute sulphuric acid, iodine wine, air, beer, limestone (impure), lime water, natural gas (impure), compounds: manganese dioxide, dry ice, ice-water mixture, ethanol, sodium carbonate, oxides: manganese dioxide, dry ice, ice-water mixture, non-metallic elements: liquid oxygen, sulfur powder, metal elements: zinc granules, magnesium bars,

Mixture: Beer Air Limestone Lime Water Natural Gas Dilute Sulfuric Acid Compounds: Ice-Water Mixture Sodium Carbonate Ethanol Manganese Dioxide Oxide: Ice-Water Mixture Manganese Dioxide Dry Ice.

Non-metallic elements: liquid oxygen, sulfur powder, iodine wine.

Mixture: Beer, Air, Ice-Water Mixture, Limestone, Lime Water, Natural Gas, Dilute Sulfuric Acid, Iodine Compounds: Sodium Carbonate, Ethanol, Manganese Dioxide, Dry Ice,

Oxide: Manganese dioxide.

Non-metallic elements: liquid oxygen, sulfur powder.

1.Same (a) O2, H2O, CO2, different staring, sugar water, air, iodine wine.

2.Same , different.

3.Yes , yes , no.

4.Homogenous elements, O2, C, H2, Na, different elements (multiple elements), CO2, H2O, NH3

5.A variety of elements of the first year (different silver elements), oxygen elements, CO2 look hard enough ah ......

I hope mine can help you. Hope.