How to judge the polarity and non polarity of a molecule in chemistry? How does it work??

A molecule is divided into two categories according to its polarity, one is a polar molecule and the other is a non-polar molecule, and the non-polar molecule is a charge that is symmetrically distributed in the molecule, such as H2, N2

CO2, CH4, etc.

Polar molecules are asymmetrically distributed charges in molecules, such as H2O, NH3, HCl, etc.

The law of their judgment is:

Diatomic elemental molecules are all non-polar molecules.

Diatomic compound molecules are all polar molecules, such as HCL, Hi, etc.

The polarity of polyatomic molecules depends on whether their spatial configuration is symmetrical, symmetrical is non-polar molecules, and vice versa, polar molecules such as NH3, H2O2 are polar molecules, and CO2, CH4, BF3 and other are non-polar molecules.

Let me introduce you to an ingenious way to determine the polarity of ABN-type molecules

Valence electronic method. First determine the valency of the central atom a and the outermost electron number of the atom a, if they are equal, then the molecule is non-polar, no.

Equal is a polar molecule.

It is also worth mentioning that the polarity of the molecule is not necessarily related to the polarity of the bond.

Elemental: Elemental molecules other than O3 are non-polar molecules.

Compounds: 1Diatomic molecular compounds are all polar molecules.

2.Triatomic molecules: Generally, except for the linear molecules of the two elements, the others are polar molecules, such as: CO2 is a non-polar molecule, SO2, HClo are polar molecules.

3.Tetraatomic molecules: Generally, except for planar regular triangular molecules, the others are polar molecules, such as: BF3 is a non-polar molecule, NH3 is a polar molecule.

4.Five-atom molecules: Generally, except for regular quadrilateral molecules, the others are polar molecules, such as: CH4 is a non-polar molecule, CH2Cl2 is a polar molecule.

The most important thing is to see whether the spatial configuration of the molecule is symmetrical, in other words, most of the molecules that can coincide with themselves when the unidirectional rotation does not exceed 180 degrees are non-polar molecules (except for planar molecules).

The polarity of the molecule is caused by the fact that the positive and negative charge centers inside the molecule do not coincide, and it is easy to judge by grasping this point and combining it with the electronegativity of the atom.

Polar molecules. The method of distinguishing it from non-polar molecules is as follows:

1. Diatomic elemental molecules are all non-polar molecules, such as hydrogen and oxygen.

2. Diatomic compound molecules are all polar molecules, such as HCL and carbon monoxide.

Wait. 3. The polarity and non-polarity of polyatomic molecules depend on whether their spatial configurations are symmetrical, symmetrical is non-polar molecules, and asymmetric tarsal bonds are polar molecules.

4. For ANBM molecules, n=1, m>1. If a valence.

Equal to the number of main groups is non-polar.

5. If the bond angle between the molecules is known, the force analysis of the molecules can be carried out.

Those with zero resultant force are non-polar molecules. Liang Dan is cautious: CO2, C2H4 and so on.

Whether there are also lone electrons (pairs) present in the intermediate particles

Like methane. ch4), four electrons are present in the outermost shell of carbon.

There is only one hydrogen outer shell, and four hydrogen isons exist in the pinned bond, and the four electrons of this electron and the carbon are "complementary" in turn to form four lone electron pairs (one lone electron pair is a combination of one hydrogen outer electron and one carbon outermost electron), so there is no extra lone electron in the outer carbon of the central particle. The four carbon-hydrogen bonds act in unison with each other, so the methane is a regular tetrahedron in the spatially distributed state.

It is a symmetrical figure and is a non-polar molecule.

Water (H2O), the central particle oxygen, the outermost shell has six electrons, hydrogen is one, two electrons of oxygen and two electrons of two hydrogens are combined, but oxygen has four electrons left, that is, there are two lone electron pairs, the lone electrons have a large force compared to hydrogen and oxygen, and the hydrogen and oxygen bonds are "squeezed" in space, so that they are on one side, and the lone electron pairs are on the other side, and the distribution of the pattern is asymmetrical in space, polar molecules. The reason for water and ethanol.

The miscibility is excellent, there is a carbon in the ethanol that connects two hydrogens, a carbon, a hydroxyl group, and the four bond forces are different, so that it is asymmetrically distributed in space, and it is a polar molecule, according to the principle of "similar miscibility", ethanol and water are both polar molecules, and the solubility is good.

The difference between memory and non-polarity mainly depends on whether there are still lone electrons in the central particle

To put it simply, it is to see whether the charge of the spring pants is symmetrical, and the term is called whether the center of the positive and pure negative charge coincides.

The most essential way to judge polar and non-polar molecules is:

A polar molecule does not coincide with the center of positive and negative charge within a molecule, and the center of positive and negative charge within a non-polar molecule is coincident.

Polar bonds exist between different elements.

A substance with a polar bond is not necessarily a polar molecule.

Methods for distinguishing between polar and non-polar molecules:

Criterion for non-polar molecules: central atom valency method and force analysis.

1. Central atom valency method:

The composition is an ABN-type compound, and if the valency of the central atom A is equal to the ordinal number of the group, the compound is a non-polar molecule. Such as: CH4, CCL4, SO3, PCL5

2. Force analysis method:

If the bond angle (or spatial structure) is known, the force analysis can be performed, and the resultant force of 0 is a non-polar molecule. Such as: CO2, C2H4, BF3

3. Diatomic molecules composed of the same kind of atoms are non-polar molecules.

Either a non-polar molecule is a polar molecule!

It is enough to know the following in high school:

Polar molecules: Hx, Co, NO, H2O, H2S, NO2, SO2, SCL2, NH3, H2O2, CH3Cl, CH2Cl2, CHCL3, CH3CH2OH

Non-polar molecules: Cl2, H2, O2, N2, CO2, CS2, BF3, P4, C2H2, SO3, CH4, CCL4, SIF4, C2H4, C6H6, PCL5, Gasoline.

2. Polar and non-polar molecules.

1 Non-polar molecules: The charges in the molecule are distributed symmetrically.

2 Polar molecules: The charges in the molecule are distributed asymmetrically in the center.

3 The relationship between the polarity of the bond and the polarity of the molecule.

Molecules composed of non-polar bonds must be non-polar molecules, such as non-metallic elemental molecules such as Cl2, F2, etc.

A molecule made up of polar bonds may be polar or non-polar.

a.Diatomic molecules composed of polar bonds must be polar molecules, such as: HCL, NO, CO, etc.

b.Polyatomic molecules made up of polar bonds may be polar or non-polar.

If the charge distribution in the molecule is centrally symmetrical, it is a non-polar molecule, such as: CH4, CO2, etc.

If the charge distribution in the molecule is asymmetrical, it is a polar molecule, such as: NH3, H2O, H2S, etc.

1. Central atom valency method: The composition is an ABN type compound, and if the valency of the central atom A is equal to the arubinization number of the group, the compound is a non-polar molecule. Such as:

CH4, CCL4, SO3, PCL5 2, force analysis method: If the bond angle (or spatial structure) is known, the force analysis can be carried out, and the resultant force is 0 for non-polar molecules. Such as:

Diatomic molecules composed of CO2, C2H4, BF3 3, and the same kind of atoms are all non-polar chain celebratory molecules. Either a non-polar molecule is a polar molecule! It is enough to know the following in high school:

Polar molecules: HX, CO, NO, H2O, H2S, NO2, SO2, SCL2, NH3, H2O2, CH3Cl, CH2Cl2, CHCL3, CH3CH2OH Non-polar molecules: Cl2, H2, O2, N2, CO2, CS2, BF3, P4, C2H2, SO3, CH4, CCL4, SIF4, C2H4, C6H6, PCL5, Gasoline Simple Judgment Methods For ANBM type n=1 m>1 If the valency of a is equal to the number of the main family, it is non-polar.

1. Polar molecules:Molecules with positive and negative charge centers that do not coincide, and polyatomic molecules with polar bonds depend on the structure.

2. Non-polar molecules:A molecule in which the center of positive and negative charge coincides.

The common types are as follows:

1. Non-polar molecules containing polar bonds, such as CO2, CS2, CH4, etc.

2. Non-polar molecules containing non-segmental slow polar bonds, such as H2, Cl2, N2, O2, etc.

3. Polar molecules containing both polar grip mode bonds and non-polar bonds, such as h-o-o-h, etc.

4. Non-polar molecules containing both polar bonds and non-polar bonds, such as h-c c-pi hunger h, etc.

Polar molecules: the positive and negative centers do not coincide, and the vector sum of the bonds is not 0. Non-polar molecules:

The positive and negative centers coincide, and the sum of the vectors of the bonds is 0. According to the synthesis and decomposition of the force, see whether the force of the central atom is balanced, if the equilibrium is a non-polar molecule; Otherwise, it is a polar molecule.

Diatomic molecules: Depends on whether the covalent bonds between the bonding atoms are polar or not.

A-B molecules (HCl): Heteronuclear diatomic molecules are polar molecules; Type A-A molecules (Cl2): Homonuclear diatomic molecules are non-polar molecules.

There are also non-polar molecules in homonuclear polyatomic molecules, such as: P4, C60, S8, B12, special note: O3 (type V) is a polar molecule.

Polyatomic molecule (ABM type): Depends on the spatial configuration of the molecule and the polarity of the covalent bond.

Valency method: When the absolute value of the valency of the central atom is equal to the number of valence electrons of the element, the molecule is a non-polar molecule; Otherwise, it is a polar molecule.

Physical model method: covalent bonds are regarded as forces, different covalent bonds are regarded as unequal forces, according to the synthesis and decomposition of forces, to see whether the central atom is balanced by force, if equilibrium is a non-polar molecule; Otherwise, it is a polar molecule.

For example, in the CO2 linear type, the two C=O bonds are symmetrical, and the bond polarity cancels each other out (F=0), and in the H2O polylinear type, the polarity of the two O-H bonds cannot be canceled out (F≠=0).