Periodic trends: understanding the exceptions
A periodic trend is not an absolute rule. Subshell structure, electron pairing and energetic details create informative exceptions.
Core idea
A periodic trend is not an absolute rule. Subshell structure, electron pairing and energetic details create informative exceptions.
Example
First ionization energies do not rise perfectly monotonically across a period: some deviations arise from p-orbital occupancy and electron pairing.
Common trap
A formula or trend is useful only when its definition and conditions of use are clear.
Check yourself
Explain the phenomenon in your own words, then identify which quantity or mechanism you would use to quantify it.
First ionization energies do not rise perfectly monotonically across a period: some deviations arise from p-orbital occupancy and electron pairing.