Long Answer TypeConsider two hydrogen atoms A and B with electron eA and eB respectively. HArepresents the nucleus of hydrogen atom A and HB represents the nucleus of hydrogen atom B.
When the two hydrogen atoms approach each other, the following two forces come into existence:
(a) Attractive interactions in between:
(i) the nucleus HA an electron eB and
(ii) the nucleus HB and electron eA
(b) Repulsive interactions in between:
(i) electron eA and electron eB and
(ii) nucleus HA and nucleus HB.
Since attractive forces overpower the repulsive forces, as a result, the enthalpy of the system decreases and a molecule of hydrogen is formed.
Enthalpy diagram: When two hydrogen atoms are at an infinite distance from each other, there is no interaction between them and therefore, the enthalpy of the system is assumed to be zero in this state (stage-A). As the two atoms start coming closer to each other, the potential enthalpy continues to decrease (stage B). Ultimately a stage is reached when the enthalpy of the system becomes minimum and hydrogen atoms are said to be bonded together to form a stable H2 molecule (state C).
The internuclear distance r0 between two hydrogen atoms at this stage is referred to as bond length. In the case of the hydrogen molecule, the bond length is 74 pm. It should be noted that two hydrogen atoms can not be brought at a distance lesser than rQ (i.e. 74 pm) because the potential enthalpy of the system increases and curve shows an upward trend (dotted lines) and molecule becomes unstable.
Give the comparison between Electrovalent (or ionic compounds) compounds and covalent compounds (special reference to properties).
Discuss the orbtial concept or quantum concept for the formation of covalent bond.
Or
Explain the formation of covalent bond on the basis of valence bond theory.
Short Answer TypeLong Answer TypeDiscuss the orbital shapes of the following covalent molecules:
(i) H2 (ii) F2 (iii) O2 (iv) N2.
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