I would like to ask a few questions about chemistry in the third year of junior high school

That is, the total number of charges carried by the individual particles in the molecule is zero. Because some particles are positively charged, and some are negatively charged, the combination must be uncharged and electrically neutral. For example, carbon dioxide c is positive tetravalent and o is negative bivalent, but there are two oxygen atoms.

Taken together, the positive and negative valence algebraic sum is zero.

It's a convention, it's a fixed format. Because the valency of each element in each substance is clear, you can know the type of substance by writing the chemical formula, and you don't need to indicate the valency.

H has only +1 valence, so n is -4 valence, and O is only -2 valence, so n is -6 valence Because n has multiple valencies You can start from an element with only one valency (ho, etc.), and use the positive and negative valency algebra of various elements of the compound to calculate the valency of n as zero.

The valence is marked at the top right of the element This is the format.

1.The molecule is electrically neutral to the outside, so the algebraic sum of the positive and negative valence of various elements is zero, and the algebraic sum is to be marked with a sign to indicate that the total amount of positive and negative charges carried by the particles that make up the molecule is equal, and the sign is opposite.

2.The chemical formula itself contains the information of valency, you should strengthen the definition of chemical formula, chemical formula is not standardized valency, standardized valency is easy for beginners to understand.

3 Generally speaking, h is +1 valence, O is -2 valence, according to this: (NH4+: 1 valence, NO3-: 1 valence).

NH4+ —x+1*4=1 solution gives x=-3 (note the symbol!) )no3- —y+(-2)*3=-1 Solution: y=+5 (with the + sign!) ）

That's a bit of a question. Embarrassed.

The first is that a compound or elemental substance is regarded as a whole, and the sum of valencies is zero, for example, H2O, oxygen is generally -2 valence, hydrogen is generally +1 valence, and the sum of the valencies of two hydrogen and one oxygen is zero. If it is simple, Fe is zero price, Cl2 is zero price, and so on.

The second question ... Well, I can only say that the elements that are oxidized and reduced in the redox reaction should be marked above the valence, in order to distinguish them from other elements, and the general chemical formula, you just think it would be simpler, and you should label it, but it doesn't make sense.

The third. nh4？Either NH3 ammonia, or NH4 + ammonium ions are not as east-east as you wrote, if it is ammonia, then please be +1 valence, there are three hydrogens is +3 valence, in order to add up to zero, nitrogen must be -3 valence.

If it is an ammonium ion, then since it is a positive ion with a positive charge, this thing adds up to +1 valence, so n is still -3 valence. What is NO3? The nitrate is (no3)2-, oxygen-2 valence, and the sum in parentheses is equal to -2, so n is +4 valence.

Friendly reminder, some knowledge does not have to know clearly, so it will only make trouble for yourself, and a little basic thing just remember to use it according to the rules.

1. For example, water H2O, H positive one valence, O negative bivalent, 2 * 1 + (-2) = 02 、......This is automatically omitted.,It's better to write it for beginners.,It's easy to write the superscript.。

3. [Isn't this really an ammonium anion......] In NH4, H is positive one price, so let n be the X price, X+4*1=-1 [Here the overall negative price] solution gets X=-5

The second ......Isn't this a minus monovalent nitrate, the same let n be the x valence, oxygen will always show negative bivalent, you can get, x+(-2)*3=-1, the solution is x=+5

So that's it =-= Ask for extra points

1. Is a substance containing metallic elements composed of ions?

No, alcl3, for example, is made up of molecules.

Does h represent two molecules? Does 2H2O mean two molecules? Help me explain by the way.

2H represents 2 hydrogen atoms because the hydrogen molecule is H2 and 2 hydrogen molecules are 2H2; 2H2O denotes two molecules.

3. What is the essential difference between sodium atom and chlorine atom? (What is the most essential difference between different atoms?) ）

The most essential difference between atoms is the number of protons, so the essential difference between them is: sodium atom has 11 protons and chlorine atom has 17 protons.

1 : Not For example, Alcl3 is a covalent compound, which is made up of molecules.

2 : 2h means 2 hydrogen atoms, not molecules, and 2h2o means 2 water molecules.

3: The number of protons is different.

1.It's not like al

2.Not 2 h molecules, but 2 h atoms, are 2 water molecules.

3.The number of protons is different.

1 is not 2h for two hydrogen atoms and 2h2o for two water molecules.

3 The number of protons of an atom.

1 Copper sulfate powder is white (anhydrous copper sulfate) Copper sulfate crystals are blue (copper sulfate pentahydrate contains crystalline water).

Both of them turn blue when they meet water because copper ions are blue in water.

2 yellow sodium peroxide, blue copper sulfate crystals, black manganese dioxide.

3 Hydrogen ions and hydroxide ions Because of the synthesis of water.

4 c Iron can replace copper, calcium oxide reacts with water to form calcium hydroxide, and acid (pH<7) undergoes acid-base neutralization reaction.

5 d nahso4 kcl

6 D Cu can produce hydrogen.

Fe can produce hydrogen.

Zn can produce hydrogen.

Mg produces hydrogen.

To get hydrogen with a substance, it is necessary to mix a substance with a higher than and a lower substance, and only d meets the criteria

1. Copper sulfate powder itself is white, but it turns blue when it encounters water. Copper sulphate crystals turn white when they lose water.

Copper sulfate powder turns blue when exposed to water, and its crystals themselves have moisture.

Yellow, sulfur powder, sodium, blue, copper sulfate solution, black, copper oxide, iron oxide, carbon.