Lecture (11) covalent bonds

Define covalent bond

The electrostatic attraction between 2 atomic nuclei and shared pair of electrons

Covalent bonds are formed

When 2 orbitals overlap

Covalent bond contains

Sigma and pie bond

Sigma bond is formed when

Spherical orbital + spherical orbital

Sigma bond is formed when

Dumbbell orbital + spherical orbital

Sigma bond is formed when

Dumbbell orbital + dumbbell orbitals head to head

Pie bond is formed when

2 dumbbell orbitals overlap side to side

Alkane contains

1 sigma bond

Alkene contains

One sigma and one pie bond

Alkyne - tipple bond

1 sigma and 2 pie bond

Covalent bond can either be

Polar or non-polar

Polar covalent bond

When electronegativities are the same or very similar

Non-polar covalent bond

When difference in electronegativity is 0.5 or more

0.5 or less

Electronegative of non-polar covalent bond

0.5 - 2.0

Electro negativity of polar covalent bond

Greater than 2.0

electronegativity of ionic bond

Non-polar bonds explanation

If the two bonding atoms are identical, their attraction of shared pair of electrons is equal. The electrons are equally distributed between bonding atoms. The bond is perfectly covalent

polar bonds explanation

if the two bonding atoms are different their attraction for the shared pair of electrons is unequal. the bonding atom with the greater attraction for the shared pair of electrons is more electronegative. the bond is polarised

example of non polar nond

H2

example of polar bond

HCL

poly atomic molecule can either be

with polar or non polar bond

polyatomic molecule with non polar bonds

P4,S8,C2H6 - resulting non polar molecule

polyatomic molecule with polar bonds resulting to a polar molecule

NH3,H2O,CHCl3

polyatomic molecule with polar bonds resulting to a non polar molecule

CCL4,CO2

explanation of polar molecules with polar bonds

polar bonds are face in the same electrons, the dipoles reinforce eachother resulting a polar molecule

explanation of non-polar molecules with polar bonds

polar bonds are arranged in symmetrical but opposite alignment, the dipoles cancel eachother, resulting a non polar molecule

dipoles cancel out

non polar molecule

dipoles reinforce eachother

polar molecule

resultant dipoles molecular

polar molecule

define electronegativity

measure of the tendency of an atom to attract a bonding pairs of electrons

pauling scale

the scale for measuring electronegativity

increase in electronegativity

above the group

increase in electronegativity

across the period from left to right

the least electronegative element

Fr

the most electronegative element

F

how can you check if the liquid is polar or non polarn

put at electrostatically charged rod next to a jet of polar liquid

the liquid will move away from rod

if liquid contains molecules with permenant dipoles

they are insoluble in water ( polar solvent)

shows they dont have ions

do not conduct electricity

all their bonding electrons are used to form covalent bond

they form hard crystals with very high melting point

due to their network of very strong covalent bond

hard crystals. with very melting point

diamond and graphite

linear molecule angle is

180

linear molecule examples

BeCl2,CO2

trigonal planar molecule angle is

120

trigonal planar molecule example

BCl3,AlCl3, any group 7

tetrahedral molecule angle is

109.5

tetrahedral molecule example

alkanes, CH4, NH4, CCL4

octahedral molecule angle is

90

octahedral molecule example is

SFe,sulfur hexa fluoride

shape of molecules with a lone pair on the central atom

V shape bent and trigonal pyramidal

V shape bent molecule angle is

104.5 or 120

V shape bent molcules examples of 104.5

H20 and H2S

V shape bent molcules examples of 120

SO2

trigonal pyramidal molecule angle is

107

trigonal pyramidal molecule examples

PCl3,NH3,CH3

shape 1 to shape 5

contain no lone pair on the central atom

shape 6 and shape 7

contains one lone pair on the central atom

CH4

tetrahedral shape with 109.5 angle, and no lone pair on the central atom

CH3

trigonal pyramidal with the angle of 107 and one lone pair on the central atom

CH3

trigonal planar shape with the angle of 120, with no lone pair on the central atom