Chemical Bonding Flashcards
A chemical bond is formed due to following two reasons
To lower down the potential energy, and to increase stability
To attain noble gas configuration by completing its octet.
Ionic bond is also known as
electrovalent Bond and non-directional bond.
Atom which is having less, electronegativity should have
low ionization energy
The atom, which is having high electronegativity should have
high electron affinity.
The alkali metals and alkaline earth metals, one combined with nonmetals form,
ionic bonds.
LiCl is having more …….. nature.
covalent
Hence, it is more soluble in pyridine and acetone
BeCl2 is also having
covalent bond.
AlCl3 is covalent and forms,
dimer are to Al2Cl6,
But in aqueous solution due to high hydration enthalpy of Al3+ and Cl- it becomes ionic in nature.
Define lattice energy.
It is the energy required to break one mole of ionic solid into its gaseous ions.
Define enthalpy of formation.
It is the energy required or released when one mole of the compound is formed from standard state of its element.
Standard state of different elements
Hydrogen is gas
Fluorine is gas
Chlorine is gas
Oxygen is gas
Sodium is solid.
Magnesium is solid
Potassium is solid
Iodine is solid
Carbon is solid
Bromine is liquid
Mercury is liquid
Calculation of lattice enthalpy is done by
Born Haber Cycle
Lattice enthalpy is proportional to
Q+Q- / r+r-
Q + is the charge of cation.
Q- is the charge of anion.
r+ is the radius of cation.
r- is the radius of anion.
Hydration enthalpy.
It is the energy released. When one mole of the compound is dissolved in excess of water.
In case of any other solvent, it is known as solvation enthalpy.
It will be always exothermic.
Hydration energy is proportional to
Q+*Q-
1/r+ * 1/r-
The compound will be soluble only if
|HE| > |LE|
Solubility is proportional to
the size difference between anion and cation.
Lesser the difference lesser will it be soluble.
Greater the difference more will it be soluble
F- and OH- are small anions.
Find the solubility order of NaCl and NaF in nonpolar solvent,
NaCl > NaF
In case of alkali metals the charge density of … is maximum
Li+ is maximum,
hence it attracts more number of water molecules and forms tertiary hydrated layre.
Hence ionic mobility of Li+ aq is least.
Hydrated ion size
Li+ > Na+ > K+ > Rb+ > Cs+
F- > Cl- > Br- > I-
Ionic Stability G1
Li+ < Na+ < K+ < Rb+ < Cs+
Ionic size G1
Li+ < Na+ < K+ < Rb+ < Cs+
Ionic mobility comparison in Li+aq and Be2+aq
Li+aq > Be2+aq
Methods to draw dot and cross structure.
Generally central atom would be the least electronegative atom.
H and F will never be the central atoms.
The number of 0H bonds will be the basicity of the acid.
When the octet of an atom is completed and the lone pair is left, it can participate in coordinate bond formation.
Between any two atoms, only one coordinate bond is possible.
Limitations of octet rule.
It was not able to explain the formation of electron deficient and species.
It was not able to explain the odd is electron molecules.
It was not able to explain the formation of super octet and expanded octet or hypervalent molecules
In case of third period elements and above in element that is in elements which can expand their octet, double bonds is preferred over coordinate bond.
Criteria to draw the bond structure
The bond structure of a molecule should explain the properties of the molecule and bond structure we are able to draw by knowing the properties.
Why does PH5 not exist?
In case of Ph5, due to less electronegativity of H atom, it is not able to excite the s orbital electrons of phosphorus into the d orbital and hence PH5 does not exist.
Same is the case with SH4 and SH6.
What is homolytic Fission?
When in a single bond one electron is accepted by each atom in fission, it is known as homolytic fission.
In this case, free radicals are formed.
Why do inert gases don’t form compounds
In case of inert gases, they do not form bond because of their octet is complete.
But in case of xenon due to its less ionization energy, it is able to form covalent bond with more electronegative elements like fluorine and oxygen.
