Error: "Fluorine has the most negative EGE." Fix: EGE(Cl) = −349 kJ/mol > EGE(F) = −328 kJ/mol. F's compact 2p orbital causes repulsion. EN and EGE are NOT the same property.

Error: "IE increases smoothly across Period 2." Fix: Two dips occur — at B (IE drops vs Be) and at O (IE drops vs N). Know both exceptions cold.

Error: "Cations are larger than their parent atoms." Fix: Removing electrons increases Zeff per remaining electron → cation is always smaller.

Error: "In isoelectronic series, more electrons means smaller size." Fix: All isoelectronic species have the same electron count. Radius decreases as proton number (Z) increases on the same electrons.

Error: "Diagonal elements are in the same group." Fix: Li–Mg (Groups 1 and 2), Be–Al (Groups 2 and 13), B–Si (Groups 13 and 14) — adjacent groups in adjacent periods.

Error: "Noble gases have negative EGE like other non-metals." Fix: Noble gases have positive EGE; it costs energy to force an electron onto a complete octet.

Error: "Group 2 elements have the most negative EGE in their period." Fix: Group 2 (filled $ns^{2}$) and Group 15 (half-filled $np^{3}$) both deviate from the trend with less negative or positive EGE.

Error: "Mendeleev's periodic law is the modern periodic law." Fix: Mendeleev used atomic mass (1869); Moseley used atomic number (1913) → Modern Periodic Law.