What is the significance of atomic number in the modern dassification of element.
help of an example:
How were the positions of isotopes of an element decided in the modem periodic table
How were the positions of cobalt and nickel resolved in the modern periodic table
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Answers
Answer:
Explanation:
The atomic number gives the number of protons in an atom. The no. of protons is equal to the number of electrons in a neutral atom. Meaning from the atomic no. we can get the number of electrons.
From the number of electrons we can get the electron arrangement
For example Sodium
No. of protons = 11
No. of electrons = 11
Electron arrangement = 2.8.1
From the electron arrangement we can now tell the group and period in which the element belong.
Group = No. of electrons in the outermost energy level
Period = No. of energy levels
Sodium has one electron in its outermost energy level (2.8.1.)
Sodium has 3 energy levels (2.8.1.)
Therefore
Sodium is in Group I and Period 3
Modern periodic table is based on atomic numbers. So, the position of isotopes of elements was decided by arranging the elements in ascending order of their atomic numbers. As isotopes have the same atomic number they do not need to be given different slots. For example, both the isotopes of chlorine,Cl-35 and Cl-37,have the same atomic number of 17,so both of them can be put at one place in the same group of the periodic table.
According to modern periodic law, elements are arranged in the order of increasing atomic numbers. The atomic number of cobalt is 27 and that of nickel is 28. So, in the modern periodic table, cobalt with lower atomic number (27) comes first and nickel with higher atomic number (28) comes later, even if their atomic masses are in the wrong order. In this way, the positions of cobalt and nickel were resolved in the modern periodic table.