Question

Ionization energy and electron affinity are defined at:
A.Enthalpy
B.Spontaneity
C.Equilibrium
D.Absolute zero

Answer 1

Hint: We can define ionization energy as the energy that is needed for the removal of one mole of electrons from one mole of isolated gaseous ion (or) isolated gaseous atom. We can say electron affinity of an atom (or) molecule is the amount of energy liberated when an electron is attached to a molecule (or) neutral atom in the gaseous state to give a negative ion.

Complete answer:
We must remember that an ionization energy is the energy that is needed for removing one mole of electrons from one mole of isolated gaseous atoms or isolated gaseous ions. The first ionization energy of an atom (or) molecule is the energy that is needed to remove one mole of electrons from one mole of gaseous atoms (or) ions.
We have to know that the ionization energy and the atomic size of an atom are inversely proportional which means that smaller the size of the atom higher would be the ionization energy.
${\text{Ionisation energy}} \propto \dfrac{1}{{{\text{Atomic size}}}}$
As we know that an electron affinity of an element is a measure of the energy released when an anion is formed from a neutral atom. Elements near fluorine tend to have the highest electron affinities. The increasing effective nuclear charge across a period explains the trends in electron affinity.
Note that this is not the same as the change of enthalpy of electron capture ionization that is defined as negative when energy is released. In other words, this change in enthalpy and the electron affinity varied by a negative sign. Overall we can say that electron affinity is a property of an atom or molecule to gain electrons and measure in negative sign of liberated energy.
At enthalpy, we can define ionization energy and electron affinity.
Therefore, option (A) is correct.

Note:
We must remember that the ionization energy of alkali metals is very low and hence, they can easily lose their outermost electron, thereby acting as a good reducing agent. We have to know that electron affinities become smaller on moving down a column of the periodic table. We can predict the reactivity of an atom using the ionization energy and it can be experimentally determined. Energy is liberated out, when an electron is added to an atom.