For 10 points, name this quantity equal to negative the standard molar enthalpy of electron gain for a gaseous monatomic element.
When constructing the Born–Haber cycle for potassium chloride, the only exothermic steps in the cycle are the step corresponding to this value for chlorine, and the "lattice energy" step involving the condensation of gaseous ions into the lattice. Chemical hardness can be approximated by one-half the difference between ionization energy and this quantity. This value increases for elements from left to right across a period, but there are many anomalies; its values for nitrogen and beryllium are negative and thus smaller than for carbon and lithium due to a stability conferred by half-filled or filled orbitals. For 10 points, name this quantity equal to negative the standard molar enthalpy of electron gain for a gaseous monatomic element.
When constructing the Born–Haber cycle for potassium chloride, the only exothermic steps in the cycle are the step corresponding to this value for chlorine, and the "lattice energy" step involving the condensation of gaseous ions into the lattice.
electron affinity [accept lattice energy or lattice enthalpy until read] &lt;Pendyala&gt;