High School Chemistry How do you compare the radius size of an atom?

For atoms: atoms of the same periodic element, the atomic radius gradually decreases from left to right; The atomic radius of the atoms of the same main group elements gradually increases from top to bottom.

For ions: in addition to conforming to the law of atomic radius progression, the comparison principles that are often examined are: 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; For particles with the same electron shell structure, the ionic radius decreases as the number of nuclear charges increases.

Atomic Radius Chemical Terminology: 1 Introduction: Atomic radius.

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, so the atomic radius data currently used is only relative and approximate. Depending on the method of determination, there are 3 types of atomic radii (1) Covalent radius:

When two atoms (which can be the same or not) are bonded by a covalent bond, the distance between the two nuclei is half. In fact, the distance between the nuclei is the bond length of the covalent bond. (2) Metal radius:

Half the distance between two adjacent metal atoms in a metal crystal. (3) Paradigm radius: Half the distance between two identical nuclei of adjacent different molecules attracted to each other by van der Waals forces.

The atomic radius magnitude is the same as the three square atomic radius.

The surface is related to the number of electron layers The number of protons in the nucleus The number of electrons (the number of protons in the nucleus = the number of nuclear charges) 1The higher the number of electron shells, the greater the atomic radius 2The more protons in the nucleus, the greater the mass of the nucleus, the stronger the ability to bind electrons, and the smaller the atomic radius

The higher the number of electrons, the larger the atomic radius Compare the size of the atomic radius of the same period Just look at the nuclear endoplasm The relationship between the atomic radius of the element and the atomic number.

The number of sublayers If the period and the group of two elements are different, then the main consideration is the number of electron shells, which is generally not related to the number of electrons in the outermost shell, and if you assume that the atom is a sphere, the diameter of the standard atom is about 10 to the 10th power meter. 2. Supplementary special note: refers to half of the effective range of atomic interaction, that is, the distance between adjacent nuclei.

In the same period of the periodic table, the closer the element is to group 0, the smaller the atomic radius, the stronger the non-metallic, and the larger the atomic number in the same major group, the larger the atomic radius.

The periodic table progressively gets larger from top to bottom and gets smaller from left to right Generally an element below has a larger radius than the element on the left.

By the periodic table, it gradually decreases from left to right and gradually increases from top to bottom (except for noble gases).

Familiarizing the periodic table is the most common method. Hard work pays off.

The following is what I picked from the notes, you need the rules are there, I hope it will help you1For atoms of the same electron shell structure (with the same period), the radius decreases with the increase of the number of nuclear charges, such as na

mg>al>si

2.For ions of the same electron shell structure.

The particle radius decreases as the number of nuclear charges increases.

Such as 02->F->Na+> Mg2+

3.For elements of the same main group (a vertical column of the periodic table).

As the number of electron layers increases, the radius increases.

Such as ffe3+ haha, that's all I have to say.

Beat me to death.

1.The comparison of the size of the atomic radius is generally judged according to the periodic table. If it is of the same period, from left to right, the radius gradually decreases as the number of nuclear charges increases; If it is of the same main group, from top to bottom, the radius increases sequentially as the number of electron layers increases.

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2.If the extranuclear electron configuration of several particles is the same, the greater the number of nuclear charges, the smaller the radius. Ruohai Education Network.

3.The radius of the anion in the ions formed by the co-periodic elements must be greater than the radius of the cations, because the number of electron layers outside the nucleus of the cations of the co-periodic elements must be one layer less than that of the anions.

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4.The more positively charged ions (the more electrons lost) the more positive metal ions formed by the same metal element, the smaller the radius.

The more electron shells an atom has, the greater the half-valence;

The number of electron shells of an ion is the same, the more protons the lower the halfprice, and the more the number of electrons, the greater the halfprice.

For atoms of the same electron shell structure (of the same period), the particle radius decreases with the increase of the number of nuclear charges, such as Na > Mg> Al>Si

For ions with the same electron shell structure, the particle radius decreases with the increase of the number of nuclear charges, such as 02->F->Na+>mg2+

For elements of the same main group (a vertical column of the periodic table) the radius increases as f as the number of electron layers increases

Atomic Radius:

As in the main group, the larger the atomic number, the larger the radius.

For the same period, the larger the atomic coefficient, the smaller the radius.

Ionic radius: The number of electron layers is different, and the more layers, the larger the radius.

The number of electron layers is the same, and the larger the number of nuclear charges, the smaller the radius.

A simple particle radius comparison is considered from the following four aspects.

1 atomic radius.

Same period: main group elements, from left to right, the atomic radius gradually decreases, such as:

Same main group: atoms of an element, from top to bottom, the atomic radius gradually increases by 2 ionic radius:

For example, Na+ F4 has the same number of electrons, and the number of protons is more, but the radius is smaller For example: F->Na+>Mg2+>Al3+

The following is what I picked from the notes, you need the rules are there, I hope it will help you1For atoms with the same electron shell structure (same period), the radius decreases with the increase of the number of nuclear charges.

Such as na>mg>al>si

2.For ions of the same electron shell structure.

The particle radius decreases as the number of nuclear charges increases.

Such as 02->F->Na+> Mg2+

3.For elements of the same main group (a vertical column of the periodic table).

As the number of electron layers increases, the radius increases.

Such as ffe3+ haha, that's all I have to say.

Beat me to death.

Atom: 1. The same main family (from left to right) decreases in order.

2。The same period (from top to bottom) increases sequentially.

Ions: 1. When the number of electrons outside the nucleus is the same, the more electrons carried the greater the radius2. When the electrons are the same, the more electrons outside the nucleus, the larger the radius.

Atoms and ions: When the same element is positively charged, the atomic radius is large; When negatively charged, the ionic radius is large.

1.With the periodic law of the elements, the same period, the atomic number is large, and the atomic radius is small.

The same main group elements, the atomic number is large, and the atomic radius is large.

2.In the periodic table, the atomic radius of the element in the lower left and upper right corners is comparable, with the lower left being larger and the upper right being smaller.

It can be inferred from the first one).

If the two elements are in the upper left corner and the lower right corner, they cannot be directly compared in size, unless they are given the data of the atomic radius, then everyone will compare

The atomic radius changes periodically as the atomic number (z) increases. In a short period, the attraction of outer electrons to the nucleus increases with the increase of atomic number, resulting in a contraction effect that gradually decreases the atomic radius. In long periods, the atomic radii of the elements in the D region decrease more slowly, and even due to the phenomenon of "lanthanide contraction", the atomic radii of the transition elements of the fifth and sixth periods of the same subgroup are nearly equal.

For the same main group element, the atomic radius tends to increase significantly from top to bottom due to the increase of the number of electron layers. The atomic radius magnitude is related to the following two aspects.

Number of electron layers. Number of protons in the nucleus.

Number of protons in the nucleus = number of nuclear charges).

The more electron layers.

the larger the atomic radius.

There are many protons in the nucleus.

Then the mass of the nucleus is large.

The ability to bind electrons is strong.

The atomic radius is smaller.

Compare the size of the atomic radius of a uniform period.

Just look at the proton Zhu in the nucleus.

Compare with a family of elements.

It depends on the number of electron layers.

If both the periods and families of the elements are different.

Then the number of electron layers is mainly considered.

It is generally not related to the number of electrons in the outermost shell.

If the atom is assumed to be a sphere, the diameter of a standard atom is about 10-8 centimeters.

To compare the magnitude of the particle radius, it can be judged by the position of the elements in the periodic table, and their judgment formula is:

The nuclei of the same layer are large and the radius of the nuclei of the same layer is large, and the nuclei of the same family are large and the radius is large.

However, this mantra can only be used to compare the size of atomic radii and to compare other particles, as long as we do so in the following order (note: where comparison is possible).

Number of electron layers. There are many electron layers and a large radius. It can be understood in this way that the electrons are arranged in layers outside the nucleus, similar to an onion, and the radius of the onion (atom) is naturally larger.

If the number of electron layers is the same, then the number of nuclear charges is compared, and if there are more nuclear charges, the radius is smaller.

Explanation: When the electron shell is the same, the more nuclear charges, the greater the attraction of the nucleus to the electrons outside the nucleus, and the nucleus naturally pulls the electrons closer! )

If the number of electron layers is still the same, then compare the number of electrons, the number of electrons is more, and the radius is large (image memory: more"Eat"One electron, then you gain weight! Explanation:

There is a repulsion force between electrons and electrons, the more electrons, the stronger the repulsion between each other, and naturally they have to occupy a larger space) sodium ion "oxygen ion" aluminum ion.

The atomic radius of a co-periodic element decreases gradually from left to right.

The atomic radius and ionic radius of the same main group elements increase gradually from top to bottom.

Ions with the same electron shell structure.

The smaller the atomic number, the larger the radius.

The cationic radius is less than its corresponding atomic radius.

The anion radius is greater than its corresponding atomic radius.

That's basically enough for you to solve the problem.

I believe that you can solve the above problems by yourself using these rules.

Compare the number of layers first.

The number of layers is large.

If the number of layers is the same.

The atomic number is small and large, so it is. alc

The noh ion rule is the same. cn

oalh

Ions of different elements of the same period.

How do radii compare?

1. The electron configuration outside the nucleus is different (that is, the number of electron layers is different), and the larger the number of electron layers, the larger the radius.

For example, the chloride ion is greater than the sodium ion.

2. When the electron configuration outside the nucleus is the same, the larger the number of nuclear charges, the smaller the radius.

For example, sodium ions are greater than magnesium ions, and sulfur ions are greater than chloride ions.

How do different ionic radii of the same element (when both are positively charged or both negatively charged) compare?

The more electrons, the larger the radius (i.e., the lower the valence, the larger the radius), such as the iron atom is larger than the divalent iron is greater than the trivalent iron, and the chloride ion is larger than the chlorine atom.

Ions of different elements of the same period.

1. The electron configuration outside the nucleus is different, and the larger the number of electron layers, the larger the radius.

2. When the electron configuration outside the nucleus is the same, the larger the number of nuclear charges, the smaller the radius.

Different ionic radii of the same element, the more electrons, the larger the radius.

I think that in the same horizontal row, the larger the atomic number, the smaller the radius: (this is because the larger the ordinal number, the stronger the ability to attract electrons, and the electrons are attracted closer together, so the radius is reduced).

And the more electron shells (homogeneous), the larger the radius.

So there are two situations to consider (same period, same family). We can't do anything about different cycles and different families.

First of all, the ion structure is the same, the difference is that the more electron layers, the larger the radius.

The same is that the larger the atomic number, the smaller the radius.

Compare the electron shell first, generally speaking, the larger the number of electron shells, the larger the ionic radius (of course, there is no comparability between some ions with too different proton numbers).

For example, the radius of br is larger than that of cl.

If the number of electron layers is the same (with the same extranuclear electron order), the number of nuclear charges (protons) is compared, and the greater the number of protons, the smaller the ionic radius.

For example, (S)2 has a larger radius than Cl.

If the electron shell structure is the same, the smaller the number of nuclear charges, the larger the radius.