Atomic structure - Shells and subshells - electronic configuration exercises

The electronic configuration of Cl is

1s², 2s², 2p⁶, 3s², 3p⁵

Na is
1s², 2s², 2p⁶, 3s¹

Cu is
1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁹, 4s²

Co is
1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁷, 4s²

Fe is
1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁶, 4s²

a) Nickel 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁸, 4s²
b) Aluminium 1s², 2s², 2p⁶, 3s¹, 3p² Aluminium is excited because the 3s subshell is not full while the 3p contains electrons.
c) Element "X" 1s², 2s², 2p⁶, 3s², 3p⁵, 4s² "X" is excited because the 3p subshell is not full while the 4s contains electrons.
d) Element "Z" 1s², 2s², 2p⁶, 3s², 3p⁶, 3d5, 4s¹ "Z" is excited because the 4s subshell is not full while the 3d contains electrons.
e) Element "Y" 1s², 2s², 2p⁶, 3s², 3p¹⁰, 3d², 4s¹ "Y" is excited because the 4s subshell is not full while the 3d contains electrons.

3) Aluminium has the atomic number 13 and a mass number of 27. Write the electronic configuration of the aluminium (Al³⁺) ion.
The aluminium ion has 10 electrons and must therefore have the electronic configuration shown below.
1s², 2s², 2p⁶

4) Write the electronic configurations of the following ions.
a) Cr²⁺
1s², 2s², 2p⁶, 3s², 3p⁶, 3d², 4s²
b) Fe³⁺
1s², 2s², 2p⁶, 3s², 3p⁶, 3d³, 4s²
c) Zn²⁺1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁸, 4s²

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The "s" and "p" electronic configuration exercises
Look at the filling of the titanium energy levels. The electronic configuration of titanium can be written as shown below. *1s², 2s², 2p⁶, 3s², 3p⁶, 3d², 4s²* Although the correct order of filling is *1s², 2s², 2p⁶, 3s², 3p⁶, 4s², 3d²,* where the 4s subshell fills before the 3d subsell, the energy levels are reversed once electrons occupy the 4s and 3d subshells and we write the electronic configuration as shown below. *1s², 2s², 2p⁶, 3s², 3p⁶, 3d², 4s²* Note. Atoms would prefer to half fill orbitals than to leave empty orbitals in a subshell. For example consider Cr with 24 electrons has the electronic configuration 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹ as opposed to 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁴, 4s² . This last electronic configuration leaves one orbital in the 3d subshell empty.
When d-block elements form ions, the 4s electrons are lost first. For example. The Cr atom has the electronic configuration 1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹ so the Cr³⁺ ion has the electronic configuration 1s², 2s², 2p⁶, 3s², 3p⁶, 3d³

Exercises Remember a few rules. - Fill from the lower energy levels first. - Avoid having empty orbitals in a subshell - d block metals form ions by losing 4s electrons first - 4s fill before the 3d 1) Write the electronic configuration of Cl (17), Na(11), Cu(29), Co(27) and Fe(26) 2) Which of the following atoms are in their electronic ground state? a) Nickel *1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁸, 4s²* b) Aluminium *1s², 2s², 2p⁶, 3s¹, 3p²* c) Element "X" *1s², 2s², 2p⁶, 3s², 3p⁵, 4s²* d) Element "Z" *1s², 2s², 2p⁶, 3s², 3p⁶, 3d⁵, 4s¹* e) Element "Y" *1s², 2s², 2p⁶, 3s², 3p⁶, 4s¹* 3) Aluminium has the atomic number 13 and a mass number of 27. Write the electronic configuration of the aluminium (Al³⁺) ion.
4) Write the electronic configurations of the following ions. a) Cr²⁺ b) Fe³⁺ c) Zn²⁺
Solution