2. Flashcards
Why do covalent bonds have low melting and boiling points?
Due to weak Vander Waal’s force of attraction less amount of heat energy is required to separate the molecule.
Why are covalent bonds non conductors of electricity ?
Due to absence of ions.
What is VSEPR theory?
According to this theory the electron pairs surrounding the central atom repel each other and move as far apart as possible so that the repulsion is minimum and stability is maximum.
Write the repulsions between electrons in descending order.
l.p-l.p>l.p-b.p>b.p-b.p
Geometry of molecules having 2 bond pairs only, give example and bond angle.
BeH2 , linear , 180
Geometry of molecules having 3 bond pairs only, give example and bond angle.
BH3 , trigonal planar , 120
Geometry of molecules having 4 bond pairs only, give example and bond angle.
CH4 , tetrahedral , 109 28’
Geometry of molecules having 5 bond pairs only, give example and bond angle.
PCl5 , trigonal bipyramidal , 120 b/w equatorial position & 90 b/w axial and equatorial position.
Geometry of molecules having 6 bond pairs only, give examples and bond angle.
SF6 , octahedral , 90
Axial bonds are weaker than equatorial bonds in PCl5. Why?
Axial bond pair suffer repulsion from 3 equatorial bond pair which increase the bond length & decrease the bond strength of axial bonds. Therefore, PCl5 readily decomposes to form PCl3 and Cl2.
Geometry of molecules having 3 bond pair and one lone pair, give example and it’s bond angle
NH3- pyramidal with 107.
Geometry of molecule having 2 bond pair and 2 lone pair, give example example and it’s bond angle.
H2O- bent with 104.
What is orbital overlap concept?
According to orbital overlap approach a covalent bond is formed by the partial overlap of half filled orbitals containing electrons with opposite spins.
What are the two types of covalent bonds?
Sigma bond and Pi Bond.
Define Sigma bond.
The types of covalent bond formed by overlapping of atomic orbitals along the internuclear axis.
