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 gaseo us atoms or ions.
You may think of ionization energy as a measure of the difficulty of removing electron or the strength by which an electron is bound. The higher the ionization energy, the more difficult it is to remove an electron. Therefore, ionization energy is in indicator of reactivity. Ionization energy is important because it can be used to help predict the strength of chemical bonds.
Ionization Energy Trend in the Periodic Table
Ionization, together with atomic and ionic radius, electronegativity, electron affinity, and metallicity, follows a trend on the periodic table of elements.
- Ionization energy generally increases moving from left to right across an element period (row). This is because the atomic radius generally decreases moving across a period, so there is a greater effective attraction between the negatively charged electrons and positively-charged nucleus. Ionization is at its minimum value for the alkali metal on the left side of the table and a maximum for the noble gas on the far right side of a period. The noble gas has a filled valence shell, so it resists electron removal.
Ionization decreases moving top to bottom down an element group (column). This is because the principal quantum number of the outermost electron increases moving down a group. There are more protons in atoms moving down a group (greater positive charge), yet the effect is to pull in the electron shells, making them smaller and screening outer electrons from the attractive force of the nucleus. More electron shells are added moving down a group, so the outermost electron becomes increasingly distance from the nucleus
@•Vike
0 Comments