How to find valency How to find valence

1. The most basic valence is the first step, and it must be mastered.

For example, the following two valency formulas:

Hydrogen, sodium, potassium, silver, positive one valent, calcium, barium, magnesium, zinc, positive bivalent, one or two copper, two three iron, two tetra iron, two tetra carbon, three aluminum, four silicon, three or five phosphorus, and manganese, chloride and nitrogen.

Potassium, sodium, hydrogen, silver, positive bivalent, calcium, magnesium, zinc, barium, positive bivalent, fluorochlorobromo, iodine negative bivalent, usually oxygen is negative bivalent, copper is positive 12, aluminum is positive, iron has positive 2 and positive, carbon has positive 2 and positive4, sulfur has negative 2, positive, 46.

After memorizing the valency formula, you have a certain foundation.

2. First mark the valency of some elements with only one valence, and then further mark the most commonly used valency of a certain element, such as oxygen, whose compounds can be negative bivalent or negative monovalent (oxygen is negative in peroxide), and finally according to the principle of positive and negative valency algebra and zero (note: to bring in the corner mark to calculate), determine the valency of unknown elements or elements with more valence.

For example: the valency of sodium bisulfite is marked: first determine that sodium and hydrogen are positive monovalent, oxygen is generally negative bivalent, and the valency of sulfur elements is more, we can calculate its valency according to the algebra of positive and negative valency algebra and zero, let the valency of sulfur be x, then there is 1+1+x+3 (-2)=0, and the solution is:

x=4, i.e., the valency of sulfur is positive tetravalent.

How to find the valency is as follows:

Valency is a property of an element that manifests itself only when the elements are compounded with each other. In a compound, the algebraic sum of positive and negative valency is equal to zero, which is the criterion for finding valency. Generally speaking, there are several ways to find the following:

1. Chemical formula or root <>

1. Find the formula for the valency of element A in the AMBN slag complex:

The valency of element b (the number of atoms of b) the number of atoms of a.

2. Find the valency formula of the elements with unknown valency in multiple compounds

The algebra of the valence of the elements with known valency and the number of atoms of the element with unknown valence.

3. Judge the valency of elements (or atomic clusters) according to the number of positive and negative charges.

In the radical formula, the algebraic sum of the positive and negative valence total valence numbers is equal to the positive and negative charge numbers carried by the radical.

Second, by the element mass ratio.

1. (The relative atomic mass of element A and the valency of element B) Hu (the relative atomic mass of element B and the valency of element) = the mass ratio of element A and the mass ratio of element B.

2. The mass ratio (or percentage composition) of element A The valency of a The relative atomic mass of a = The mass ratio of element B (or percentage composition) The valency of b The relative atomic mass of B.

Third, by the mass ratio.

The valency of b is the relative atomic mass ratio of a) (the valency of a is the relative atomic mass ratio of b) = the mass ratio of element a and the mass ratio of element b.

Multiply the valency of each element by the number of atoms, and the result is equal to zero.

For example: H2O (+1)*2+(-2)*1=0If the valency of one of the elements is known, then the valency of the unknown element can be set as x

If it is known that the valency of element O in H2O is -2, and the valency of element H is found, then (x)*2+(-2)*1=0 is solved to obtain the price of x=+1 h element at +1 valence.

Problem 1: How to find valency In a compound, find the valency of an element based on the fact that in a compound, the algebraic sum of the valency of * is equal to zero.

For example: +m -n

a p b q

m) x p + n) x = 0

Find the valency of S in the compound CuSO4.

According to the compound, the valency of Cu is +2, the valency of O is -2, and the valency of S is x plus.

Then: (+2) + x + 2) x 4 = 0

Solution: x = 6

Question 2: How to find valency First of all, you must memorize the valency formula of common elements:

monovalent potassium hydrochloride sodium silver; divalent oxygen, calcium, barium, magnesium, zinc; 3. Aluminum, 4 silicon, 5 nitrogen and phosphorus; 246 sulfur should be remembered;

two or three irons; two-four carbon; Copper-mercury bivalent is the most common;

The "valency" of ionic roots: monovalent hydroxide nitrate; divalent carbonate sulfate; Trivalent only phosphate; The positive price is ammonium.

Then, the algebraic sum of the positive and negative valencies in the chemical formula must be equal to zero is used to calculate.

For example, the valency of iron in iron oxide is +3;Since the total valence state of the three oxygen atoms is -6, then the total valence state of the 2 iron atoms is +6, but it is 2 iron atoms, then each iron atom is +3.

According to the algebraic sum of the valence of the chemical bai is zero, only the chemical dao of one of the elements can be found through the chemical du formula

Valency, the internalized valency of the other elements must be known capacitance.

For example, N2O3, where O is known to be -2 valence, let the valency of N be N, 2N+3X(-2)=0

n=+3Na2SO3, find the valency of S, because H is +1 and O is -2, let the valency of S be N2X(+1)+N+3X(-2)=0

n=+4

The valency of each element in the chemical formula is 0

In junior high school chemistry, the cross method is used to write chemical formulas based on valency, such as the chemical formula of a substance formed by the combination of aluminum and oxygen.

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

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.

The Alo chemical formula is Al2O3

3. Check the correctness 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

After giving the formula, if you know the valency of an element, you can multiply its valency by the number of atoms of its molecule. Since the valency of the valency is zero, subtract the previous valency from zero and divide it by the number of atoms in the molecule to obtain the valency of another element.

The valency of the two elements is given, and the least common multiple of the valence is found. Then divide the least common multiple by the valency 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.

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

1) There are positive and negative valences in the valence;

1) Oxygen is usually -2 valence.

2) Hydrogen usually shows +1 valence.

3) When metallic elements are combined with non-metallic elements, metallic elements show positive valence and non-metallic elements show negative valence.

4) Some elements can show different valencies in different substances.

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

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

If the chemical formula of a substance is known, the valency of the known element can be marked first, and calculated according to the principle that the algebraic sum of the valency of the elements in the compound is zero. Such as na

sio3，na

is known to be +1 valence, o

Yes -2 valence +1*2+x+(-2*3)=0

x=+4 when the element and the valency of the element are known, write the positive element on the left and the negative valence element on the right, and also according to the principle that the valence algebra sum of the elements in the compound is zero, the diagonal intersection method is used to mark the number of atoms, if the value is 1, it can be omitted.

Writing of alumina: The first step is to write al

o, re-standardizing valence left + 3, right - 2, because the sum is not 0, the diagonal intersects, and it is written as alo