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SUBJECT-CHEMISTRY
CHAPTER-Periodic classification of element
SUBTOPIC- Ionisation enthalpy, electron gain
enthalpy,electronegativity,valency and diagonal relationship.
KEY NOTES :
Ionization enthalpy :
The minimum amount of energy required to remove the most loosely bound
electron from an isolated gaseous atom so as to convert it into cation is
called its ionization enthalpy.
Successive ionization enthalpy :
rd
nd
st
The energy required to remove 1 , 2 , 3 electrons from an isolated gaseous
atom are called successive ionization enthalpies.
Factors on which ionization enthalpy depends :
(i)Nuclear charge :
If the nuclear charge is more then ionization enthalpy of the element is
more.
Atomic size :
If atomic size increases, effective nuclear charge decreases. So ionization
enthalpy decreases.
Screening or shielding effect :
The decrease in effective nuclear charge due to the presence of electrons in
inner shell is called shielding effect.
More the shielding effect, less the attractive force, so ionization
enthalpy decreases.
Penetration of subshell :
