Valency Vs Oxidation Number

Valency	Oxidation Number
It is the combining capacity of an atom. It is expressed as the number of hydrogen atoms or double the number of oxygen atoms with which an atom of the element combines.	It is the residual charge which an atom has or appears to have when all the atoms are removed as ions.
Since it refers to combining capacity, it is a whole number only. As such it does not carry any plus or minus sign. For example, in NH3, the valency of nitrogen is 3 and that of hydrogen is 1.	Since it refers to charge, it can be positive, negative or zero. For example, in NH3, nitrogen has oxidation number of -3 and that of hydrogen is +1.
Valency of an element cannot be zero (except for noble gases).	Oxidation number of an element can be zero. For example, oxidation number of C in CH2Cl2 is zero.
Since atoms always combine in whole numbers, valency of an element is always a whole number.	Oxidation number may have fractional values. For example, oxidation number of S in Na2S4O6 is +2.5.
In general, elements like C, N and S exhibit constant valency. Thus, valency of N in all its compounds is three.	Even the elements C, N and S exhibit variable valency. For example, the oxidation number of N (given in brackets) in its compounds vary from +5 to -3 as: N2O5(+5), NO2(+4), N2O3(+3), NO(+2), N2O(+1), N2(0), N2H4 (-2) and NH3(-3).

Electron Gain Enthalpy Vs Electronegativity

Electron Gain Enthalpy	Electronegativity
It is the tendency of an isolated gaseous atom to attract an electron.	It is the tendency of an atom in a molecule to attract the shared pair of electrons.
It is the property of isolated atoms.	It is the property of a bonded atom.
It is the absolute electron attracting power of an atom.	It is the relative attracting power of an atom.
It can be experimentally measured.	It cannot be measured experimentally. It is only a relative number.
It has units such as kJ mol-1 or eV/atom.	It has no units. There are only scales for comparison.
The electron gain enthalpy of an atom is constant.	The electronegativity of an atom is not constant. It depends upon the oxidation state of an atom, hybridization state of the atom and the nature of substituents attached to it.

Inductive Effect Vs Electromeric Effect

Inductive Effect	Electromeric Effect
It is a permanent effect which involves slight drifting of shared σ-electrons towards more electronegative atom.	It is a temporary effect which involves complete transfer of π-electrons to one of the bonded atoms.
It operates only in saturated compounds which contain at least one polar bond.	It operates in unsaturated compounds which contain at least one multiple bond which may be polar or non-polar.
It does not need any outside reagent for its operation.	It operates only in the presence of an outside reagent.
It involves a partial separation of charges without formation of ions.	It involves complete transfer of electrons from the reagent to substrate and vice versa. As a result of this effect, ions are formed.

Schottky Defect Vs Frenkel Defect

Schottky Defect	Frenkel Defect
It is produced because of missing atoms or ions from their normal crystal sites.	It is produced when some atoms or ions are displaced from their normal sites and occupy interstitial sites.
The presence of Schottky defect lowers the density of the crystal.	It does not affect the density of the crystal.
It is generally shown by ionic solids having high co-ordination number and in which cations and anions are of equal sizes e.g., NaCl, CsCl.	It is generally exhibited by ionic solids having low co-ordination number and in which anions are larger in size than cations e.g., AgCl, ZnS.

Reversible Process Vs Irreversible Process

Reversible Process	Irreversible Process
The process in which the direction may be reversed at any stage by merely a small change in a variable like temperature, pressure, etc.	A process in which the direction cannot be reversed at any stage by change in a variable like temperature, pressure, etc.
In a reversible process, the driving force is only infinitesimally greater than the opposing force at all stages.	The driving force is different than the opposing force.
It is carried out infinitesimally slowly.	It is carried out rapidly.
At any stage during the process, equilibrium is not disturbed.	Equilibrium may exist only after the completion of the process.
It is only imaginary and cannot be achieved in actual process.	All natural processes are irreversible.
Work obtained in this process is maximum.	Work obtained in this process is not the maximum.

Sigma Bond Vs Pi Bond

Sigma (σ) Bond	Pi (π) Bond
A sigma bond is formed by the end to end filled atomic orbitals along the internuclear axis. The overlapping involves two s-orbitals, one s and p-orbital or two p-orbitals.	A pi-bond is formed by the sidewise overlap of two half-filled p-orbitals.
In this case, the overlapping can take place to a larger extent and therefore, the bond formed is a strong bond.	In the formation of π-bond the overlapping occurs to a lesser extent and therefore, the bond is weak.
The molecular orbital is symmetrical about the internuclear axis.	The molecular orbital is discontinuous and consists of two charged clouds above and below the plane of atoms.
There can be free rotation of atoms around the σ-bond.	Because of overlapping of the electron clouds above and below the plane of the atoms, free rotation of atoms around π-bond is not possible.
The bond may be present between two atoms either alone or along with π-bond.	The bond is always present between two atoms in addition to sigma bond.
In the formation of sigma bond, s-orbitals can participate.	s-orbitals cannot participate in the formation of pi-bond.