Question

Put the following elements in order of increasing first ionization energy (lowest to highest): S, Ca, Mg,

CI

Answer 1

Answer: Ca, Mg, S, Cl

Explanation: general trends are IE increases as the number of electrons in the outermost shell, and decreases as the number of shells (and shielding effect) increases.

S outer 6, shells 3

Ca outer 2, shells 4

Mg outer 2, shells 3

Cl outer 7, shells 3

Ca has 2 outer, 4 shells —> lowest

others have 3shells

Mg 2outer, S 6, Cl 7