Why are the properties of elemental chemistry related to atomic radius?

Second, let's talk about the same main family.

1.The electron shell increases, and the atomic radius increases:

We know that as the number of atomic numbers increases, so does the number of electrons outside the nucleus, and we also know that electrons are distributed in different electron shells, and the larger the period, the more electron shells there are, and the larger the atomic radius. Take F and Cl as examples, F has two electron shells and Cl has three, so the radius of Cl is larger.

2.The electron layer increases, and the ability to attract external electrons decreases:

According to the above, we know that the number of electron layers increases, the radius increases, and why the ability to attract external electrons decreases, there are two reasons:

According to Coulomb's law, when r increases, f decreases.

Some people will ask, although R is increasing, Q is also increasing, and it is increasing rapidly, why is this happening?

Outer electrons have a repulsive effect on external electrons: don't ignore the outer electrons, they are powerful characters. According to the principle of same-sex repulsion and opposite-sex attraction, although the nucleus of an atom is attractive to external electrons, the outer electrons are repulsive to external electrons.

The more layers and the more electrons, the stronger the repulsion to the external electrons, so the two forces are gradually canceled out, so the attraction will also decrease.

For example, F and Cl, F has two electron shells, while Cl has three electron shells, and the third electrons of Cl have repulsion to external electrons, which greatly weakens the attraction of the nucleus to external electrons, so it is naturally less easy to get electrons.

3.Ability to gain electrons and ability to lose electrons:

After the above, we already know that the more electron layers, the weaker the ability to attract external electrons, and the weaker the ability to obtain electrons, so the non-metallic properties gradually weaken. On the contrary, the stronger the ability to lose electrons, the metallicity naturally increases. This is also the reason why the later the cycle, the more metals.

The next day, CL walked on the road with the joy of defeating NA, but unfortunately ran into F, CL was very afraid of F, so he quickly avoided it, but F only said: "I am the strongest in the world!" "Just shook the cl away.

Alas, poor cliché.

If the radius is large, the binding force will be small, and the outer electrons will not be easy to be controlled, which is very vivid, so do you think the chemical properties will not be lively? Something like na than li is an example.

The chemical properties of an element mainly depend on the number of electrons in the outermost shell of the atom, such as sodium, the outermost electron is 1 electron, so it is extremely easy to lose this electron and become a sodium ion to reach an 8-electron stable structure;Another example is neon, the outermost shell is already 8 electrons, and the structure is already very stable, so it itself is also very stable and not easy to react.

The difference in chemical properties is manifested as the difference in the action of atoms on electrons outside the nucleus.

The smaller the radius of the same main group element, the stronger the force on the electrons outside the nucleus, and the easier it is to obtain electrons, which is manifested as the strength of electronegativity.

The same period is the effect on the electrons outside the nucleus, and the higher the same period, the larger the radius, the more volatile the electrons, and vice versa.

This is related to the number of electrons in the most shell of the atom.

The atomic radius of an element is determined by both the number of protons and the number of electrons. The chemical properties are mainly determined by the valence electrons, and the valence electrons of the main group elements are generally the outermost electrons, while the secondary group elements mostly also include some electrons in the secondary outer shell. Atomic radius is one of the parameters that describes the size of an atom.

Extension: According to different scales and measurement methods, the definition of atomic radius is different, the common ones are orbital radius, van der Waals radius (also known as paradigm radius), covalent radius, metal radius, etc. The atomic radius of the same atom can vary greatly depending on the definition, so when comparing the relative sizes of different atoms, the data** must be consistent.

The atomic radius is mainly affected by two factors: the number of electron layers and the number of nuclear charges. In general, the higher the number of electron layers, the smaller the number of nuclear charges, and the greater the atomic radius. This also makes the atomic radius of Songfan have an obvious periodic degeneration law on the periodic table.

The radius of the original trembling cherry tree has a great influence on the chemical properties of the element, so the study of the atomic radius is of great significance and value in the development of chemistry.

It usually refers to half of the distance between two adjacent nuclei as measured experimentally. Theoretically, there is no strictly fixed orbit of electrons outside the nucleus, so there is no strict boundary for the size of the atom, and the radius of a single atom cannot be accurately determined. Depending on the method of measurement, there are 3 types of atomic radii.

Atomic angle: 1. The atomic radius of the atom of the element in the same week excavation period gradually decreases from left to right

2. The atomic radius of the atoms of the main group elements gradually increases from top to bottom.

Ionic angle: 1. Compared with the atoms and ions of the same element, the cation is smaller than the corresponding atomic radius, and the anion is larger than the corresponding atomic radius

2. For particles with the same electron shell structure, the ionic radius decreases with the increase of the number of nuclear charges.

The law of atomic radius:

1. Except for the first period, the atomic radius of other periodic elements (except noble gas elements) decreases with the increase of atomic number;

2. The atomic radius of the elements of the same group increases from top to bottom with the increase of the number of electron layers. (except for sub-families during the 5th and 6th cycles).

In the same period, from left to right, the number of electrons outside the nucleus of the element is the same, the number of electrons in the outermost shell increases sequentially, and the atomic radius decreases (except for group zero elements). The ability to lose electrons is gradually weakened, the ability to gain electrons is gradually increased, the metallicity is gradually weakened, and the non-metallic ability is gradually enhanced.

The highest positive oxidation number of an element increases from left to right (except for those without positive valence), and the lowest negative oxidation number increases from left to right (except for the first period, except for the O and F elements in the second period).

In the same family, from top to bottom, the number of electrons in the outermost shell is the same, the number of electrons outside the nucleus gradually increases, the atomic radius increases, the atomic number increases, the metallicity of the element increases, and the non-metallic decreases.

The ionic radius refers to the radius of the electron cloud within an atom, and the ionic radius of an element changes in comparison to its atomic radius. This void leak is due to the fact that atoms produce ions due to the transfer of electrons during the synthesis process, and the radius of the ions is generally smaller than the radius of the atom.

Since the magnitude of the radius of the ion is an important factor affecting the properties of the compound, the ionic radius determines the properties of the elemental compound. Generally speaking, the smaller the ionic radius, the stronger the interaction, so the melting point, boiling point, solubility and other properties of the compound will be greater. In addition, the ionic radius also affects the crystal junction and composition of the compound, so it also affects the conductivity, magnetism, and thermodynamic properties of the compound.

Ionic radius is a measure of the density distribution of electrons around the nucleus of an atom, and it indicates the size of an ion. The shape of the electron density distribution can be described by the ionic radius. Ions with a smaller ionic radius have a higher electron density, which means they have a relatively dense electron cloud.

This also means that these ions are more reactive because their electrons react more easily with other atoms or molecules.

This is also the reason why the ionic radius can be used to determine the properties of elemental compounds. For example, when the ionic radius of two elements is very different, the compounds between them are usually unstable. For example, sodium hydroxide (NaOH) is a common compound that consists of sodium ions and oxygen ions.

Due to the small ionic radius of sodium ions, it has greater reactivity and can therefore react with oxygen ions to form NaOH compounds. If the ionic radius difference between the two elements is smaller, then the compounds between them are usually stable. For example, aluminum chloride (AlCl3) is a common chemical compound composed of aluminum ions and chloride ions.

Since the ionic radius of the aluminium ion and the chlorenvy ion are not much different, the AlCl3 compound is stable.

1. If the number of electron layers is different, the ionic radius with a large number of electron layers is large;

2. If the number of electron layers is the same, the radius of the small number of protons is large;

3. According to the periodic table of chemical elements;

In the same group, the atomic radius generally increases from top to bottom, because the number of electron layers increases from top to bottom, so the atomic radius increases. The main and secondary elements change very differently. From top to bottom, the radius of the main group elements increases without exception, but the magnitude of the increase decreases.

For example, Zr and HF, Nb and Ta, Mo and W, their atomic radii are very close, which is mainly due to the shrinkage of the lanthanides. Lanthanide contraction refers to the phenomenon that the atomic radius of lanthanides shrinks from LA to LUs.

Factors influencing atomic radius:

The first is the number of nuclear charges, the greater the gravitational pull of the nucleus on the electrons outside the nucleus (causing the electrons to shrink towards the pronucleus), the smaller the atomic radius; When the number of electron layers is the same, the atomic radius decreases with the increase of the number of nuclear charges.

the second is the number of outermost electrons, the more the outermost number of electrons, the larger the radius;

The third is the number of electron shells (the hierarchical arrangement of electrons is related to the size of the space near and far from the nucleus and the mutual exclusion between the electron clouds), the more electron shells, the larger the atomic radius. When the electron shell structure is the same, the larger the number of protons, the smaller the radius.

The above content refers to: Encyclopedia - Atomic Radius.