On the other hand neon, the noble gas, immediately preceding it in the periodic table, requires 2081 kJ/mol or 21.56 eV/atom. Ionization energy increases across a row on the periodic maximum for the noble gases which have closed shells.įor example, sodium requires only 496 kJ/mol or 5.14 eV/atom to ionize it.Ionization energy is lowest for the alkali metals which have a single electron outside a closed shell.Therefore the electronegativity is greatest at the top-right of the periodic table and decreases toward the bottom-left. Elements with high ionization energies have high electronegativities due to the strong pull exerted by the positive nucleus on the negative electrons. Electrons with low ionization energies have low electronegativities because their nuclei do not exert a strong attractive force on electrons. Ionization energy is is related with electronegativity and electron affinity. In general, the ionization energy increases moving up a group and moving left to right across a period. Helps to understand reactivity of elements (especially metals, which lose electrons). For example, only 7.38 eV is required to remove the outermost electron from a lead atom, while 88,000 eV is required to remove the innermost electron.

Some of these electrons are more tightly bound in the atom than others. The electrons that circle the nucleus move in fairly well-defined orbits. There is an ionization energy for each successive electron removed. It is related to the atoms electronegativity and electron affinity. The first ionization energy, I 1, is the energy needed to remove the first electron from a neutral atom. The nth ionization energy refers to the amount of energy required to remove an electron from the species with a charge of ( n-1). The ionization energy of an atom or ion is the minimum energy required to remove an electron from the ground state of the isolated gaseous atom or ion. The ionization energy associated with removal of the first electron is most commonly used. Another trend seen in the periodic table is electron affinity.Electron affinity is a measure of the energy released when a neutral atom in the gas phase gains an electron and forms a negatively charged ion ().While ionization energies may be measured with great precision, electron affinities are not as easy to measure.

Where X is any atom or molecule capable of being ionized, X + is that atom or molecule with an electron removed (positive ion), and e − is the removed electron.Ī Iodine atom, for example, requires the following ionization energy to remove the outermost electron. Ionization Energy Versus Electron Affinity. Ionization energy, also called ionization potential, is the energy necessary to remove an electron from the neutral atom. First Ionization Energy of Iodine is 10.4513 eV. The 1st ionization energy of the element M is a measure of the energy required to remove one electron from one mole of the gaseous atoms M.

Ionization energy periodic table