9th science
Structure of The Atom
Arrangement of electrons in an atom – Electronic Configuration
The maximum number of electrons can be obtained by 2n2; where ‘n’is the orbit number. Thus after knowing the maximum number of electrons for a particular shell, the arrangement of electrons in an atom can be identified. It is called Bohr Bury Schemes.
Rules to write the electronic configuration of an atom
- Maximum number of electrons in an orbit is calculated by 2n2, where ‘n’ is number of orbit and may be equal to 1, 2, 3 , . . . .
- Electrons occupy the next orbit only after filling the inner orbit completely.
- The maximum number of electrons in outermost orbit will not be more than 8.
Electronic configuration of Hydrogen
Atomic number of hydrogen = 1
Therefore number of electrons = 1
Maximum number of electrons in 1st orbit = 2
Since, hydrogen has only one electron, therefore, it will reside in 1st orbit.
Thus electronic configuration of hydrogen
Number of orbit present in hydrogen = 1
Electronic configuration of Helium
Atomic number of helium = 2
Therefore number of electrons = 2
Therefore, electronic configuration of helium is
Number of orbit in helium atom = 1
Electronic configuration of Lithium
Atomic number of Lithium = 3
Therefore number of electrons = 3
Since the maximum number of electrons in 1st orbit is equal to 2, therefore, after accommodating 2 electrons in 1st orbit, the third electron will go in 2nd orbit.
Thus, electronic configuration of lithium is
Number of orbit in Lithium atom = 3.
Electronic configuration of Beryllium
Atomic number of beryllium = 4.
Therefore number of electrons = 4.
Thus, electronic configuration of Beryllium is
Number of orbit in beryllium = 2
Electronic configuration of Boron
Atomic number of boron = 5
Therefore number of electrons = 5
Thus, electronic configuration of boron is
Number of orbit in boron = 2