propeety of ionization enthalpy
Answers
Ionization energy is the energy required to remove an electron from a gaseous atom or ion. The first or initial ionization energy or Ei of an atom or molecule is the energy required to remove one mole of electrons from one mole of isolated gaseous atoms or ions.
Ionization Enthalpy. Ionization Enthalpy of elements is the amount of energy that an isolated gaseous atom requires to lose an electron in its ground state. Losing of electrons results in the formation of cations. The first ionization energy of element A is the energy required by an atom to form A+ ions.
It is because of the shielding effect that the ionization energy decreases from top to bottom within a group. From this trend, Cesium is said to have the lowest ionization energy and Fluorine is said to have the highest ionization energy (with the exception of Helium and Neon)
Thus ionization energy is always positive, since every single electron is bound and thus has negative energy! What might not be positive is electron affinity. It is a different quantity, defined as the energy released when an atom captures an electron and becomes a negative ion.