Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.
Define ionisation enthalpy. Discuss the factors affecting ionisation enthalpy of the elements and its trends in the periodic table.
Ionisation enthalpy or Ionisation energy:
Ionisation energy is the amount of energy required to remove the valence electron from an isolated gaseous atom in its ground state.
In this the amount of energy required to remove the first outermost electron is called first ionisation enthalpy and that which is required to remove the second most loosely bound electron is called second ionisation enthalpy and like so.
M(g)→M+(g)+1e− (I.E.)1
M+(g)→M+2(g)+1e− (I.E.)2
Factors on which Ionization enthalpy depends are discussed below:
Atomic Size: As the size of an atom increases, the force of attraction between the nucleus and the outermost electron decreases and hence the ionization energy decreases. Similarly, as size decreases, ionisation energy increases.
Ionisation enthalpy∝1/ Atomic size
Nuclear charge: As the nuclear charge of the atoms having same number of energy shells increases, the ionisation energy increases.
Ionisation enthalpy∝Nuclear charge
Screening effect: It correspond to the repulsion of the outer shell electron (which undergo ionisation) due to inner core electron. As this effect decreases the attraction between nucleus and valence electron increases and hence the ionisation energy increases.
Ionisation enthalpy∝1/ Screening effect
Shape of orbital: The s-orbital is more close to nucleus than the p-orbital of the same orbit. Thus, it is easier to remove electron from a p-orbital in comparison to s-orbital. In general, the ionisation enthalpy follows the following order (s>p>d>f) in orbitals of the same orbit.
Half filled and fully filled orbitals: The atoms having half filled and fully filled orbitals are comparatively more stable, hence more energy is required to remove the electron from such atoms. The ionization enthalpy is rather higher than the expected value in case of such an atom.
Ionisation enthalpy∝Stable electronic configuration
Trend of ionisation enthalpy in the periodic table:
In periodic table, the ionisation energy decreases down the group due to increase in atomic size (or decrease in effective nuclear charge).
Whereas, the ionisation energy increases across the period from left to right, again due to decrease in atomic size (or increase in effective nuclear charge) from left to right.
Ionisation enthalpy or Ionisation energy:
Ionisation energy is the amount of energy required to remove the valence electron from an isolated gaseous atom in its ground state.
In this the amount of energy required to remove the first outermost electron is called first ionisation enthalpy and that which is required to remove the second most loosely bound electron is called second ionisation enthalpy and like so.
M(g)→M+(g)+1e− (I.E.)1
M+(g)→M+2(g)+1e− (I.E.)2
Factors on which Ionization enthalpy depends are discussed below:
Atomic Size: As the size of an atom increases, the force of attraction between the nucleus and the outermost electron decreases and hence the ionization energy decreases. Similarly, as size decreases, ionisation energy increases.
Ionisation enthalpy∝1/ Atomic size
Nuclear charge: As the nuclear charge of the atoms having same number of energy shells increases, the ionisation energy increases.
Ionisation enthalpy∝Nuclear charge
Screening effect: It correspond to the repulsion of the outer shell electron (which undergo ionisation) due to inner core electron. As this effect decreases the attraction between nucleus and valence electron increases and hence the ionisation energy increases.
Ionisation enthalpy∝1/ Screening effect
Shape of orbital: The s-orbital is more close to nucleus than the p-orbital of the same orbit. Thus, it is easier to remove electron from a p-orbital in comparison to s-orbital. In general, the ionisation enthalpy follows the following order (s>p>d>f) in orbitals of the same orbit.
Half filled and fully filled orbitals: The atoms having half filled and fully filled orbitals are comparatively more stable, hence more energy is required to remove the electron from such atoms. The ionization enthalpy is rather higher than the expected value in case of such an atom.
Ionisation enthalpy∝Stable electronic configuration
Trend of ionisation enthalpy in the periodic table:
In periodic table, the ionisation energy decreases down the group due to increase in atomic size (or decrease in effective nuclear charge).
Whereas, the ionisation energy increases across the period from left to right, again due to decrease in atomic size (or increase in effective nuclear charge) from left to right.
