The energy needed to remove an electron from a gaseous atom or ion is called ionization energy. An atom or molecule’s first or initial ionizing energy or Ei is the energy needed to remove a mole of electrons from a mole of isolated gaseous atoms or ions.
You might think of ionizing energy as a measure of the electron removal difficulty or the force by which an electron is bound. The higher the energy of ionization, the harder it is to remove an electron. Therefore, the energy of ionization is in the reactivity measure. Ionization energy is important as it can be used to help predict chemical bond strength.
Also known as: ionization potential, IE, IP
units: ionizing energy is measured in kilojoule units per mole (kJ / mol) or electron volts (eV).
Ionization Energy Trend in the Periodic Table-
Ionization follows a pattern on the periodic table of elements along with atomic and ionic size, electronegativity, electron affinity, and metallicity.
Ionizing energy generally increases the motion of the component (row) from left to right. This is because the atomic radius usually decreases moving over a period resulting in a greater efficient attraction between the negatively charged electrons and the positively charged nucleus. Ionization is the minimum value for the alkali metal on the left side of the table and the maximum value for the noble gas on the far right side of the table. The noble gas has a full valence shell, so it can tolerate the removal of electrons.
Ionization decreases the movement of the element group (column) from top to bottom. This is because the outermost electron’s main quantity increases moving down a group. There are more protons in atoms which pass down a group (greater positive charge), yet the effect is to draw in the shells of electrons, make them smaller and shield outer electrons from the nucleus ‘ attractive power. Further electron shells are introduced going down a group, thereby gradually distancing the outermost electron from the nucleus.
First, Second, and Subsequent Ionization Energies-
The first ionization energy is the energy needed to remove the outermost valence electron from a neutral atom. The second energy of ionization is the one needed to remove the next electron, and so on. The second energy of ionization is always lower than the energy of the first ionization. Take an alkali metal atom, for example. It is fairly easy to remove the first electron because its removal gives the atom a stable shell of electrons. The removal of the second electron requires a new shell of electrons closer to and nearer to the nucleus of the atom.
The hydrogen’s first ionizing power can be expressed by the following equation: H(g) + H+(g)+e-°=-1312.0 kJ / mol
Exceptions to the Ionization Energy Trend-
Two exceptions to the trend are readily apparent when you look at a chart of first ionization energies. Boron’s first ionizing energy is less than beryllium’s, and oxygen’s first ionizing energy is less than nitrogen’s.
Due to the electron structure of these elements and the law of Hund, the explanation for the difference. The first potential ionization electron for beryllium comes from the orbital 2s, although boron ionization involves a 2p electron. The electron comes from the 2p orbital for both nitrogen and oxygen, but the spin is the same for all 2p nitrogen electrons, whereas in one of the 2p oxygen orbitals there is a set of paired electrons.
Ionization energy is the total amount of energy needed to remove an electron from an atom or ion. Kilojoules per mole (kJ / M) and electron volts (eV) are the most common units of ionization energy.
Ionization energy on the periodic table shows periodicity.
The general trend is to increase the ionization energy movement over an element period from left to right. Moving over a period of time from left to right, atomic radius decreases, thus attracting electrons to the (closer) nucleus.
The general trend is to decrease ionization energy moving down a periodic table unit from top to bottom. A valence shell is inserted to move down a band. Further from the positively charged nucleus, the outermost electrons are easier to remove.
Also Read – Electron configuration
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