How to write the chemical formula of a compound based on valency?

Beginners can write a chemical formula by first writing the atoms or clusters of atoms that make up a compound and marking their chemical valences on the head, for example.

c o and then cross the values above them, write 4 below o and 2 below c, and you have c2o4

Then there is the chemical formula of carbon dioxide CO2 in the initial stage of another special substance is H2O2 hydrogen peroxide (hydrogen peroxide), because O2 is a peroxide atom group Apparent-2 valence needs to be taken together and cannot be reduced.

For the simplest integer ratio, let's take an example.

Si is a +4 valence element, nitrogen has -3 valence, and the chemical formula they make up is Si3N4 (the normal valence is written first).

That is, dividing the least common multiple of the valency of two elements by the valency of the element is the element corner marker.

Let's take another example: n is +3 valence, oxygen is -2 valence, nitrogen trioxide, the least common multiple of n and o is 6, so the corner mark of nitrogen is 2, and oxygen's is 3, so nitrogen oxide is n2o3

Ca is +2 valence Chlorine is -1 valence Least common multiple is 2 So calcium chloride is CaCl2 Hope it can help you

The lower corner mark is multiplied by the valence to be the least common multiple of the two elements, and the rest depends on the situation.

In junior high school chemistry, the criss-cross method is used to write chemical formulas such as the chemical formulas of substances formed by the combination of aluminum and oxygen according to valency.

1. Write the element symbols in the order of positive elements before negative valence elements.

2. Write the valence cross directly above the element symbol, write 2 in the lower right corner of al, and write 3 in the lower right corner of o.

3-2alo

The chemical formula can be done, ie.

AL2O33, check the correctness or falsehood of the chemical formula according to the algebraic sum of the positive and negative valencies of each element in the chemical formula is zero.

A correct chemical formula is written by the cross method, but when writing the chemical formula by the cross method, it is necessary to pay attention to ensure that the valence of the two elements is a prime number of each other.

3. If the valency of two elements is not a prime number, for example, the chemical formula of the oxide of sulfur with +6 valence.

After marking the valency above the element symbol, take the absolute value and divide it to get 3:1, and write it in the lower right corner of the element symbol to get SO3

How to write the chemical formula of alumina: , before the metal, after the non-metal, and after the oxygen in the oxide, write: al o; Mark the valency directly above the element symbol, and write 2 in the lower right corner of al and 3 in the lower right corner of o

Alo can be extracted to obtain the chemical formula as: Al2O3; Check the correctness or falsehood of the chemical formula according to the "algebraic sum of the positive and negative valencies of each element in the chemical formula is zero": (+3) 2+( 2) 3 0.

Such a correct chemical formula is written in the criss-cross method.

The chemical formula is: Al2O3; Check the correctness or falsehood of the chemical formula according to the "algebraic sum of the positive and negative valencies of each element in the chemical formula is zero": (+3) 2+( 2) 3 0.

Such a correct chemical formula is written in the criss-cross method.

Calculate the chemical formula of sodium chloride, it can be seen that Na is positive and Cl is negative and 1+(-1)=0, and the positive valence is written in the front and negative in the back, which is NaCl

Calculate the chemical formula of iron oxide, we can know that iron +2 or +3, and it is iron oxide, not ferrous iron, it can be known that it is **iron + 3 valence, oxygen -2 valence, 3 2 + (-2 3) = 0, so the chemical formula is Fe2O3

Pure originality, please be sure to support the landlord!

Metallic ions are all positive, and most of the non-metallic ions are negative.

The highest positive valence of a non-metallic element is its outermost electron number, and the lowest negative valence is the highest positive valence minus 8

For example, the highest positive price of Cl is 7 (HCO4) and the lowest negative price is -1 (HCL).

After giving the formula, if you know the valency of an element, you can multiply its valency by the number of atoms of that element in its molecule. Since the valency of the valency is zero, the product of the previous valency and the number of atoms of the element is subtracted from zero and divided by the number of atoms of the other element in the molecule to obtain the valency of the other element.

The valency of the two elements is given, and the least common multiple of the absolute value of the valency is obtained. Then divide the least common multiple by the absolute valence value to find the number of atoms in the molecule.

The valency is expressed in +1, +2, +3, -1, -2 ...... for positive and negative valence0 and so on should be marked directly above the element symbol. (e.g. ).

To determine the valency of the elements in a compound, attention should be paid to.

1) There are positive and negative valences.

2) Oxygen is usually -2 valence.

3) Hydrogen usually shows +1 valence.

4) When metallic elements and non-metallic elements are combined, metallic elements show positive valence, and non-metallic elements show negative valence (generally speaking, the positive valence is written in the front, and the negative valence is written in the back).

5) Some elements can show different valencies in the same substance.

6) The algebraic sum of positive and negative valencies in a compound is 0

7) The valency of an element is a property exhibited by the atoms of an element when forming a compound, so in an elemental molecule, the valency of an element is 0

Generally, the rise and fall of valency is used to balance the redox reaction equation.

Steps: mark the price change, find the change, find the total number, and allocate the coefficient. Namely.

1) Marking the beginning and end states of the valency of the changing elements;

2) Find the number of changes in the price increase element or the price reduction element (regardless of the front and the back) (3) Find the least and least common multiple of the price increase and the price reduction change, which are used as the coefficients of the oxidant or reducing agent, respectively.

4) Equalize the valence element, using the valence part of the valence element first and then the non-valence part of the valence element.

5) Trim other elements by observation;

6) Check whether the equation after trim conforms to the law of conservation of mass (the ion equation also depends on whether it conforms to the conservation of charge).

Calculation according to the valence should be observed"The sum of the valencies of the elements is equal to zero".For example, in BaCl2, the valency of Ba is +2 valence, and Cl is generally -1 valence in the compound

2*1+(-1x)=0.Find x=2(Note:.)

Usually, you can calculate it directly orally, so you don't have to be so troublesome).

Remember: the valency of a single element is zero.

Writing the correct chemical formula is also calculated according to the valence, but the reverse calculation is just the opposite, and the same is observed"The sum of the valencies of the elements is equal to zero".

Valence formula.

Hydrogen +1, Oxygen-2, Silver, Lithium, Sodium, Potassium +L, Zinc, Magnesium, Calcium, Barium +2, Aluminum +3, Silicon +4

Only metal or hydrogen, nitrogen, phosphorus-3, sulfur-2, chlorochlorobromide-iodine total -1

Variable price, not terrible, specific judgment"and zero".

If the element is zero, it should be remembered.

A chemical formula is a formula that uses element symbols to represent the composition of matter, and the sum of the relative atomic masses of each atom in the chemical formula is the quantity of the formula.

H2 is elemental when it is written alone, so h is +1, 2 hydrogen atoms are +2 valence, o is -2, there are 4 oxygen atoms, so o4=-8, so s=-8+2=-6

h +1s=-6

o = -2 looks.

Answer, support me.

Start by addressing the question of why you want to put parentheses.

When you first learn chemistry, you need to be exposed to chemical terms. First of all, there is the chemical element symbol h o c n fe cu al and the like, and then you will come into contact with the chemical formula. to describe in chemical language, write the names of these substances.

The above symbols are both elemental symbols and atomic symbols, and you can imagine them as the names of these atoms.

So atoms can form clusters of atoms, which are things that atoms come together to form -- and you can imagine thinking of a cluster of atoms as an atom.

Well, with this knowledge, you will be able to understand. Think with common sense.

Several atoms combine to form molecules. We write the molecular formula and use parentheses in order not to cause misunderstandings and troubles.

For example, if we write na0h without parentheses, we will write na0h without parentheses, because a na is accompanied by an oh. And do not write corner mark 1. But ca(oh)2 because ca has two ohs (it doesn't matter why).

If the parentheses are removed, caoh2 will cause misunderstanding.

A few atoms, with a few atoms, are marked in the bottom right corner. As for the specific ratio, it depends on the valence. Make the algebraic sum of valency zero.

And I guess there's going to be basic copper carbonate in those 63 chemical formulas. You can understand it.

Cu2(OH)2 CO3 Cu stands for Copper atom It is not an atomic group without parentheses, but it is necessary to add a corner mark 2 (OH-) is an atomic group and the number is 2, so add parentheses CO3 2- (3) is a cluster of carbonate atoms, but the number is 1, without parentheses. As for why you have to ask why the chemical formula is this. But it's just a matter of being able to tell that it's right.

The valency of Cu is +2 and there are two that are 2*(+2)=+4

The valency of oh- is -1 and there are two that are 2*(-1)=-2

The valency of CO3 2- is -2 and has a 1*(-2)=-2

Algebraic sum to 0 That's it. The same goes for everything else.

If you ask how the valency of an atomic cluster is determined, for example, oh- o is -2 h is +1 natural and is -1

no3 - n is +5 o is -2 *3 = -6 and is -1

CO3 2- c is +4 o is -2 *3 = -6 and is -2

As for what you're told about, the product of valency and the number of molecules, it's actually the number of atoms or the number of clusters of atoms, which is what I did above.

In junior high school, all molecules are electrically neutral, that is, if you touch them, they will not be electrocuted, which explains why algebraic sums are zero. For example, water H2O.

Finally, I want to say that the corner mark in the lower right corner represents the particles in a molecule (particles are atomic clusters of ions......Count, in layman's terms. It's not too hard.

There will usually be an element that has only one valence. Based on this element, the number of other elements is determined, and the chemical formula is written.

Are you talking about 3 or more than 3? 3 kinds are relatively easy to say. Variable price?

How much has it changed? Generally, only one of the three elements is variable, and the specific problem is analyzed, you see that the elements in nitric acid cannot be zero price, right? There is only n to change, and the composition may also be nitrous acid, and there is not only one, but if you take the test, it will not be said that only one is right.

The valence is determined according to the number of electrons outside the nucleus, and the valence is determined according to the activity when the element has a variable valence.

The sum of positive and negative valency is 0, so find the least common multiple of the valency number, and then find a way to match the positive charge with the least common multiple and the negative charge with the least common multiple!

Have you learned to write chemical formulas according to valency.