Question

Write short notes.
d. Mendeleev's periodic law.
b. Structure of the modern periodic
S table.
c. Position of isotopes in the
Mendeleev's and the modern
periodic table.​

Answer 1

Answer:

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1. Mendeleev's periodic law.

The law that the properties of the elements are periodic functions of their atomic numbers. Also called Mendeleev's law. (originally) the statement that the chemical and physical properties of the elements recur periodically when the elements are arranged in the order of their atomic weights.

2. Structure of the modern periodic S table.

In the modern periodic table, the elements are arranged in the order of their inreasing atomic number. In the modern periodic table there are seven horizontal rows called periods and eighteen vertical columns (1 to 18) called groups. The arrangement of the periods and groups results into formation of boxes.

3. Position of isotopes in the Mendeleev's and the modern periodic table.

Isotopes have similar chemical properties but different masses. Based on periodic law an isotope is an element which must have a separate place in periodic table. However there are ni places fir isotopes in Mendeleev periodic table. Since isotopes have same atomic number they haven't been given any specific position in modern period table.

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Answer 2

Answer:

• Mendeleev's periodic table

1. elements are arranged in increasing order of their atomic masses.
2. It is not divided into any blocks.
3. Therefore are 8 groups.
4. Isotopes could not be placed properly.

• Modern periodic table

1. Elements are arranged in increasing order of their atomic numbers.
2. It is divided into four blocks, namely s-block,p-block,d-block and f-block.
3. There are 18 groups.
4. Isotopes occupy the same position as the element.

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