Write accurate electronic configurations applying Aufbau, Pauli, and Hund's rules, including exceptions.
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An orbital filling diagram (boxes with arrows) is necessary to visualize Hund's rule and Pauli exclusion.
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Define Aufbau, Pauli Exclusion, and Hund's Rule.
Writing the electronic configuration of an atom means distributing its electrons into various orbitals. To do this correctly, we follow three fundamental rules that dictate the order and behavior of electrons in the ground state.
Write the configuration for Nitrogen and Sodium.
Let's practice writing electronic configurations using the principles of orbital filling. For Nitrogen (Z=7), we need to fill 7 electrons starting from the lowest energy orbital. The complete configuration is . Now consider Sodium (Z=11), which has 11 electrons. Following the Aufbau principle, its full configuration is . We can also write this using the noble gas core notation. The first 10 electrons correspond to the noble gas Neon, so the simplified configuration for Sodium is [] .
Explain Chromium and Copper configurations.
While the Aufbau principle works perfectly for most elements, there are some notable exceptions in the periodic table. The most famous occur in the transition metals, specifically Chromium (Cr) and Copper (Cu).
Determine the number of unpaired electrons in specific atoms.
State the final numerical count for both elements.
Write out the subshell configurations and justify your counts using Hund's rule and any known exceptions.
Why do unpaired spins matter in physical properties?