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Why do Thevenin's theorem and Norton's theorem have different zero setting methods for voltage source and current source when calculating equivalent resistance? one
This is called removing the source, removing the power supply, leaving only the resistor
To remove the voltage source u is to let u = 0, the voltage is the potential difference, and the potential difference equal to zero is the short circuit;
In the same way, if I divide is, i.e. i.s = 0, i.e. i.s = 0 does not form a closed loop, i.e. I.S. I.S. I.S. I.S. I.S. I.S. I.S. I.S. I.S. I
The arrangement rule of the same horizontal elements in the periodic table is: from left to right;;;;;;
With the increase of atomic coefficient, the number of outermost electrons increases,
The law of the periodic table of elements should be complete
1、 Atomic radius
In the same period (except for rare gases), from left to right, with the increase of atomic number, the radius of element atoms decreases;
In the same family, from top to bottom, the atomic radius increases with the increase of atomic number
2、 Main valence (highest positive valence and lowest negative valence)
In the same period, from left to right, with the increase of atomic number, the highest positive valence of elements increases (from + 1 valence to + 7 valence), except for the first period and O and f elements in the second period;
Except for the first cycle of the lowest negative valence increasing (from - 4 to - 1), since metal elements generally have no negative valence, it starts from group Ⅳ a
The sum of the absolute value of the highest price and the absolute value of the lowest price is 8
3、 Metallic and nonmetallic properties of elements
In the same period, from left to right, with the increase of atomic number, the metallicity of elements decreases and the non metallicity increases;
In the same family, from top to bottom, with the increase of atomic number, the metallicity of elements increases and the non metallicity decreases;
4、 Oxidizability and reducibility of simple substance and simple ion
In the same period, from left to right, with the increase of atomic number, the oxidizability of elemental substance increases and the reducibility decreases; the reducibility of corresponding simple anion decreases and the oxidizability of simple cation increases
In the same group, from top to bottom, with the increase of atomic number, the oxidizability of elemental substance decreases and the reducibility increases; the reducibility of corresponding simple anion increases and the oxidizability of simple cation decreases
The stronger the reducibility of elements, the stronger the metallicity; the stronger the oxidation of elements, the stronger the non metallicity
5、 Acidity and basicity of hydrate corresponding to the highest valence oxide
In the same period, from left to right, the acidity of the hydrate corresponding to the highest valence oxide increases (the alkalinity decreases);
In the same group, from top to bottom, the alkalinity of the hydrate corresponding to the highest valence oxide of the element increases (the acidity decreases)
6、 How easy it is to combine simple substance with hydrogen
In the same period, from left to right, with the increase of atomic number, it is easier for the elemental to combine with hydrogen;
In the same family, from top to bottom, with the increase of atomic number, the more difficult it is to combine elemental with hydrogen
7、 Stability of gaseous hydrides
In the same period, from left to right, the stability of gaseous hydrides increases with the increase of atomic number;
In the same family, the stability of gaseous hydrides decreases with the increase of atomic number from top to bottom
In addition, there are some criteria for judging the metallic and nonmetallic properties of elements, which can be used as a supplement to the periodic law of elements
With the change of valence orbitals from left to right from empty to full, elements change from mainly metallic to mainly nonmetallic
In the same group of elements, the higher the period is, the higher the energy of valence electron is, and the easier it is to lose. Therefore, the elements at the bottom are generally more metallic than those at the top
The stronger the alkalinity of the highest valence hydroxides, the stronger the metallicity of the elements; the stronger the acidity of the highest valence hydroxides, the stronger the non metallicity of the elements
The more stable the gaseous hydrides of elements, the stronger the nonmetallic properties
The elements of the same family have similar properties
Theoretically, atoms with the same valence electron configuration have the same tendency to gain or lose electrons, which is the reason why the same group of elements have similar properties
The above rules are not applicable to noble gases
Regularity of periodic table of elements
To find the law of the periodic table of elements is more complete than from left to right and from bottom to top, from right to left and from top to bottom
The periodic table of elements is the concrete form of the periodic law of elements expressed in tables. It reflects the internal structure of elements and the law of their mutual relations. The periodic table of elements is called periodic table for short. There are many forms of expression in the periodic table of elements. At present, the most commonly used one is Werner's long periodic table
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