The essence of the periodic law of elements: the periodicity of electron configuration outside the nucleus determines the periodicity of elements.
Contents of periodic law of elements:
Schematic diagram of atomic radius change I. Atomic radius
In the same period (except rare gases), from left to right, with the increase of atomic number, the atomic radius of elements decreases;
In the same family, from top to bottom, with the increase of atomic number, the atomic radius of elements increases.
Second, the main price (the highest positive price and the lowest negative price)
In the same period, from left to right, with the increase of atomic number, the highest valence of other elements is increasing (from+1 to +7) except O and F elements in the first and second periods.
The lowest negative price increases (from -4 to-1), except for the first period. Since metal elements generally have no negative valence, they start from group Ⅳ a.
III. Metallic and nonmetallic elements
In the same period, from left to right, with the increase of atomic number, the metallicity of elements decreases and the nonmetal increases;
In the same family, from top to bottom, with the increase of atomic number, the metallic properties of elements increase and the nonmetallic properties decrease;
Fourthly, redox of simple substance and simple substance ion.
In the same period, from left to right, with the increase of atomic number, the oxidation of simple substance increases and the reducibility decreases; The reducibility of simple anions is weakened and the oxidation of simple cations is enhanced.
In the same family, from top to bottom, with the increase of atomic number, the oxidation of simple substance is weakened and the reduction is enhanced; The reducibility of corresponding simple anions is enhanced, and the oxidation of simple cations is weakened.
The stronger the reducibility of simple substance, the stronger the metallicity; The stronger the elemental oxidation, the stronger the nonmetal.
5. Acidity and alkalinity of hydrate corresponding to the highest valence oxide.
At the same time, the acidity of hydrate corresponding to the highest valence oxide of this element increased (alkalinity decreased);
In the same group, the alkalinity of the hydrate corresponding to the highest valence oxide of this element is enhanced (the acidity is weakened).
Six, the difficulty of combining simple substance with hydrogen
In the same period, from left to right, with the increase of atomic number, simple substance is easier to combine with hydrogen;
In the same family, from top to bottom, with the increase of atomic number, simple substances are more difficult to combine with hydrogen.
Seven. Stability of gaseous hydrides
In the same period, from left to right, with the increase of atomic number, the stability of gaseous hydride of elements is enhanced;
In the same family, from top to bottom, with the increase of atomic number, the stability of gaseous hydride of elements decreases.
In addition, there are some criteria for judging the metallic and nonmetallic nature of elements, which can be used as a supplement to the periodic law of elements:
With the gradual change of valence orbits from left to right, from empty to full, the elements are mainly changed from metal to nonmetal.
With a group of elements, the higher the period, the higher the energy of valence electrons, and the easier it is to lose, so the elements below are generally more metallic than the elements above.
The higher the basicity of the highest valence hydroxide of an element, the stronger the metallicity of the element; The stronger the acidity of the highest valence hydroxide, the stronger the nonmetal of the element.
The more stable the gaseous hydride of elements is, the stronger the nonmetal is.
Elements in the same family have similar properties.
Atoms with the same valence electron configuration have the same tendency to gain or lose electrons in theory, which is why the properties of the same group of elements are similar.
The above laws do not apply to rare gases.
There are also some conclusions based on the periodic law of elements:
The stronger the metallicity of an element, the smaller its first ionization energy. The stronger the nonmetal, the greater the affinity of the first electron.
In the same periodic element, the more empty the orbit, the easier it is to lose electrons, and the more full the orbit, the easier it is to gain electrons.