How to tell if an organic substance is a polar or non polar molecule

Molecules are divided into two categories according to their polarity, one is polar molecules.

One is non-polar molecules, which are symmetrically distributed in the molecule by charge, such as H2, N2CO2, 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, CO2, CH4, BF3 and so on are non-polar molecules.

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

Valence electronic method. First, the valency of the central atom a is determined.

and the outermost number of electrons of an atom.

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.

There are two convenient ways to do this.

1.Look at the valency of the central atom.

If it's the most**.

Then it is a non-polar molecule.

Otherwise, it is a polar molecule.

For example, the central atom of SO2 is S

S is the most ** is +6

So this one is a polar molecule.

The original word for the center of SO3 is also S here

So it is a non-polar molecule.

2.See if there are lone pairs of electrons in the central atom.

If there is, it is a polar molecule.

Such as NH3 if the above two methods cannot be distinguished.

That can only depend on the structure.

Symmetrical things are non-polar molecules.

Asymmetrical are polar molecules.

The methods for distinguishing polar molecules from non-polar molecules are 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, carbon monoxide, etc.

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

4. For ANBM molecules, n=1, m>1. If the valency of a is equal to the number of the main family, it is non-polar.

5. If the bond angle between the molecules is known, the force analysis of the molecules can be carried out, and the non-polar molecule with zero resultant force is the non-polar molecule. Such as: CO2, C2H4 and so on.

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.

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.

3. Judgment of molecular polarity:

The polarity of a molecule is determined by both the polarity of the covalent bond and the spatial configuration of the molecule.

Judgment on polar molecules and non-polar molecules1、A diatomic molecule composed of polar bonds (covalent bonds formed by different kinds of atoms) must be polar molecules. Such as: CO, NO, HF, HBR, HI, HCL, etc.

2. A diatomic molecule composed of non-polar bonds (covalent bonds formed between atoms of the same kind) must be non-polar molecules. Such as: H2, O2, N2, F2, Cl2, B2, I2, etc.

3. Polyatomic (three or more atoms) molecules composed of polar bonds may be polar or non-polar. (1) If it is an ABN or BNA type molecule, the key is to see whether the electrons on the outermost shell of the central atom (atom A) are provided to form a covalent bond with the B atom. If the electrons on the outermost shell of atom A are provided to form a covalent bond with atom B, the molecule is non-polar; Such as:

CO2, CH4, BF3, SO3, CS2, PCL5, CCL4, etc. If the electrons on the outermost shell of atom A are not all provided to form a covalent bond with atom B, the molecule is a polar molecule; Such as: H2S, H2O, NH3, PCL3, SO2, etc.

2) Some polyatomic molecules composed of polar bonds can be judged based on the configuration of the molecule. For example, CH3CL, CH2CL2, and CHCL3 are asymmetrical tetrahedra, so they belong to polar molecules.

4. If the above three conditions are not met, it can be judged according to the principle of solubility of similar ones (the solute composed of polar molecules is easily soluble in the solvent composed of polar molecules, and the solute composed of non-polar molecules is easily soluble in the solvent composed of non-polar molecules). For example, H2O2, ethanol, acetic acid, etc. are soluble in water, and water is a polar molecule, so they are also polar molecules; C2H4, C2H2, C6H6, gasoline, white phosphorus, noble gases, etc., are insoluble in water, so they are non-polar molecules.

I wish you success in your studies!!

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.

In the composition of ABN-type compounds, if the valency of the atom A before the central destruction is equal to the ordinal number of the group, the compound is a non-polar molecule, otherwise it is a polar molecule, such as CCL, SO, PCL, and the diatomic molecules composed of the same silver atoms are non-polar molecules.

Common types of bonds for polar molecules:

1. Non-polar molecules containing polar bonds, such as CO, CS, CH, etc.

2. Non-polar molecules containing non-polar bonds, such as H, Cl, N, O, etc.

3. Polar molecules containing both polar 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-h, etc.

The positive and negative charge centers in the molecule do not coincide, and the distribution of the charge is uneven and asymmetrical from the perspective of the whole molecule, and such a molecule is a polar molecule.

The positive and negative charge centers coincide in the dividing scatter, and from the perspective of the whole molecule, the charge distribution is uniform and symmetrical, and such a molecule is a non-polar molecule.