A method for quickly judging ionic bonds and polar non polar covalent bonds

1. Ionic bonds.

Ionic bonds are formed by the transfer of electrons (cations for those who lose electrons and anions for those who gain electrons). That is, the chemical bond formed between the positive and negative ions due to the electrostatic attraction. Ions can be single ions, such as Na+, Cl-; It can also be formed from clusters of atoms; Such as SO4 2-, NO3-, etc.

The ionic bond has a strong force, no saturation, and no directionality. The minerals formed by ionic bonds are always in the form of ionic crystals.

2. Covalent bond The formation of a covalent bond is the pairing of electrons with opposite spin directions between two adjacent atoms, at which time the atomic orbitals overlap each other, and the density of the electron cloud between the two nuclei increases relatively, thereby increasing the gravitational attraction to the two nuclei. The covalent bond has a strong force and is saturated and directional. Because only electrons with opposite spin directions can be paired to form bonds, covalent bonds are saturated; In addition, when atomic orbitals overlap each other, the symmetry condition and the maximum overlap condition must be satisfied, so the covalent bond is directional.

Covalent bonds can be further divided into:

1) Non-polar covalent bond The electron cloud that forms a covalent bond is located right in the middle of the two atoms that are bonded, such as the c-c bond of diamond.

2) Polar covalent bond The electron cloud that forms a covalent bond is biased towards an atom with a greater attraction to the electron, such as a Pb—S bond, and the electron cloud is biased to the S side, which can be expressed as Pb S.

1.Polar covalent bond: a covalent bond formed by the sharing of electron pairs between different kinds of atoms, and the atomic electrons are obviously biased towards the strong non-metallic one, which is a polar covalent bond, referred to as a polar bond.

For example, in the HCl molecule, Cl is much more non-metallic (oxidizing) than H, so the electrons are obviously biased towards Cl, and Cl is negative. 2.

Non-polar bonds can exist in elemental molecules (such as H-H bonds in H2, O=O bonds in O2, N-n bonds in N2), and compounds composed of two non-metallic elements with relatively symmetrical molecular structures also have non-polar covalent bonds (e.g., BF3, C2H2, SO3, CH4, CCL4, SIF4, C2H4, C6H6, PCL5, etc.). Teach you an easy way:

As long as the molecular structure is not symmetrical, it is a polar bond. Follow-up question: Which of the molecules are symmetrical?

How can you tell that? For example: hf,,na2o2,sif4...

For example, Hf, an H atom is larger than F atom, and it is asymmetrical, which is a polar covalent bond molecule. For example, CH4, if you look at the molecular structure of methane, it is symmetrical with C atom as the center, so it is a non-polar covalent bond. For example, NH3 is a polar covalent bond molecule, because the ammonia molecule has a pair of isolated electrons, which causes the molecule to be not symmetrical, so it is a polar covalent bond.

For example, Na2O2 is an ionic compound, which must be a polar molecule.

Such as SIF4, the same principle as methane, non-polar covalent bonds. Also tell you a simple way: the principle of similar dissolution, in most cases, gas molecules.

If it can be dissolved in water in large quantities, it is a polar molecule, because water is polarOtherwise, it is non-polar! Like HCl, HF, etc., which can be dissolved in water in large quantities, isn't it a polar molecule?

I want to judge quickly.

First of all, it is necessary to have a good knowledge of chemical bonds.

Then look at mine.

Specific steps and methods.

1 Judge from small to large.

First determine whether it is an ionic bond or a covalent bond.

1 Seeing the elements of the first main group and the second main group, then they are generally ionic compounds with ionic bonds2 all are non-metallic elements, generally are covalent compounds, have covalent bonds (ammonium salts are removed), 3 acids, all are covalently bonded.

Make the above judgment first.

After that, the polarity of the covalent bond is judged.

Remember this sentence :

To form a non-polar bond, the bonding atom must be the same element.

Whereas, having the same element does not necessarily have a non-polar bond.

It means that the elements on both sides of the bond are the same, generally non-polar bonds, the elements are not the same, and they must be polar bonds.

Different atoms on both sides can also be non-polar bonds. Let's talk nonsense. If you don't understand, you still teach people, and you misunderstand people's children.

Ionic bond. The building between the molecules of soluble substances has the weakest force, such as sodium chloride.

The construction between the molecules is the ionic bond, which is destroyed when it encounters water, and there are no sodium chloride molecules in the water, only chloride ions and sodium ions. This equilibrium is the equilibrium in which the positive and negative cancellations of the two particles.

Covalent bond. It is two or more atoms that use a few electrons together to reach a stable state, and these electrons play the role of connecting atoms. This equilibrium is the equilibrium of common electrons, so it is called a covalent bond. Such as carbon dioxide.

Carbon dioxide does not separate carbon atoms and oxygen atoms when dissolved in water because covalent bonds are much stronger than ionic bonds.

Polar bonds and non-polar bonds are for covalent bonds, assuming that atom A and atom B are combined by electron q to form a covalent bond, if A and B are the same atom, such as hydrogen, they have the same attraction to electrons, so the electrons are in the middle, and will not be biased towards a certain atom to produce an electrode, and this covalent bond is called a non-polar bond. If A and B are not the same atom, such as water, a covalent bond is also formed between his oxygen atom and hydrogen atom, but the hydrogen atom and the oxygen atom have different electron attraction in the middle, causing the electrons to be closer to the oxygen atom, so the charge is asymmetrical on the channel of the oxygen atom and the hydrogen atom, resulting in an electrode, which is called a polar bond.

If the bonding atom is an atom of the same element, a non-polar bond is formed, otherwise a polar bond is formed;

If the bonding electron pair is not biased towards a certain bonding atom, a non-polar bond is formed, otherwise a polar bond is formed;

If the bonding atom is not electrically conductive, a non-polar bond is formed, otherwise a polar bond is formed.

Without considering the delocalized and coordination keys, the method and method are essentially equivalent.

The method cannot be used as a basis for judgment, because an atom can form multiple covalent bonds with the same atom and different kinds of atoms at the same time, and a polar bond can be formed between an atom and different kinds of atoms, thus showing electricality, and a non-polar bond can be formed between an atom of the same species, so that an atom with electrical properties can form a non-polar bond, that is, the method misjudges.