PrayogX › Chemistry › Classification of Elements and Periodicity

Periodic properties: ionisation reversal, isoelectronic radii, alkali densities and bond strength

Strip electrons off boron and carbon to find where the second-ionisation trend reverses, shrink an isoelectronic series by adding protons, weigh a cubic centimetre of each alkali metal and break H-H against F-F.

Sub-topics covered

• Successive ionisation enthalpies and cation configurations
• Isoelectronic ionic radii
• Densities of the alkali metals and the Na-K inversion
• Bond dissociation enthalpy of the halogens and the F-F anomaly
• Effective nuclear charge and shielding

What it teaches

• The second ionisation removes an electron from the cation, not the atom
• A filled subshell in the cation makes the next ionisation expensive
• Within an isoelectronic set the radius falls as the nuclear charge rises
• Density is a ratio, so a faster-growing volume can outrun a growing mass
• Lone-pair repulsion on small atoms weakens a single bond

Simulation ID

• ADV-2026-P2-CHE-Q07 · revision 1

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