Ionization Energy Trend
Part of the Atomic Structure section of Coddy's Chemistry journey. Lesson 39 of 45.
The first ionization energy is the energy needed to remove the outer electron. Down a group it falls, because the electron is farther away: Li 520, Na 496, K 419 kJ/mol.
Across a period it rises, because more protons hold the electrons tighter. But period 3 has two dips.
First ionization energy (kJ/mol) across period 3: up overall, with dips at Al and S
Al is lower than Mg: its electron is the first in 3p, higher than 3s. S is lower than P: its fourth 3p electron pairs up, and paired electrons repel.
Challenge
Period 3 runs from sodium to argon. Put Na, Mg, Al, Si, P, S, Cl and Ar in order of first ionization energy, the lowest first.
Try it yourself
Test yourselfThis lesson includes a short quiz. Start the lesson to answer it and track your progress.
All lessons in Atomic Structure
1Matter and Atoms
What Everything Is Made OfElements, Compounds, MixturesChemical SymbolsCounting Atoms in a FormulaRecap - Molecule Kit