Chemistry Formulas for Chemical Bonding

Chemistry Formulas for Chemical Bonding

 

   1.       Necessary condition for an ionic solid to be dissolved in water

                                Hydration Energy > Lattice Energy

   2.       Order of melting and boiling points of certain compounds

NaF > NaCl > NaBr > NaI;    MgO > CaO > BaO

3.       No Bond is 100% Ionic

4.       Force of attraction between two oppositely charged ions in vacuum (air) as per Coulombs Law

F = q₁q₂/r²

5.       Order of the Lattice Energy of some compounds

·         LiX > NaX > KX > RbX > CsX    (where X = F, Cl, Br, I)

·         MgO > CaO > SrO > BaO

·         MgCO₃ > CaCO₃ > SrCO₃ > BaCO₃

·         BaSO₄ > SrSO₄ > CaSO₄ > MgSO₄  

·         Mg(OH)₂ > Ca(OH)₂ > Sr(OH)₂ > Ba(OH)₂

·         Bivalent Ions-Bivalent Ions > Univalent Ions-Bivalent Ions or Bivalent Ions-Univalent Ions > Univalent Ions- Univalent Ions

6.       Example of some compounds which contains more than one type of bond

·         NaOH, KOH, Na₂CO₃  (Ionic Bond, Covalent Bond)

·         CO, NH₃.BF₃, [Co(NH₃)₃Cl₃]  (Dative Bond, Covalent Bond)

·         NH₄Cl, CuSO₄, K₄[Fe(CN)₆], [Cu(NH₃)₄]SO₄  (Dative Bond, Ionic Bond, Covalent Bond)

·         CuSO₄.5H₂O  (Hydrogen Bond, Dative Bond, Ionic Bond, Covalent Bond)

7.       Double bond or triple bond is always shorter than corresponding single bond

8.       As S-Orbital is smaller than P-Orbital so bond length decrease with increase in S-character

SP³  C-H  =  1.093 Å (as in Alkanes)

SP²  C-H  =  1.087 Å (as in Alkenes)

SP  C-H  =  1.057 Å (as in Alkynes)

9.       Bond length increases if size of bonded atom is increases with given atom

HI > HBr > HCl > HF

10.   Bond distance is directly proportional to Atomic size

11.   Order of bond strength (or bond energy) of different hydrogen halides

H-F > H-Cl > H-Br > H-I

12.   Bond energy is directly proportional to bond order

Triple Bond > Double Bond > Single Bond

13.   Formula of Dipole Moment

Dipole moment (µ) = Electronic Charge (e) x Distance (d)

14.   Unit of Dipole Moment

Debye (D)

1D = 1 x 10^-18e.s.u. cm

SI unit of Dipole Moment is = Coulomb-Meter (C-m)

1D = 3.336 x 10^-30 C-m

15.   Dipole Moment of some substances

Substance with Formula	Dipole Moment (D)
HF	1.91
H2O	1.84
SO2	1.60
NH3	1.46
NF3	0.24
CH3Cl	1.86
HCl	1.03
H2S	1.10
HBr	0.78
HI	0.38

16.   Formula to calculate percentage ionic character of covalent bond

% Ionic Character = (Observed dipole moment x 100)/Dipole moment for 100% ionic bond

17.   Order of polarizing power of cations

Li⁺ > Na⁺ > K⁺ > Rb⁺ > Cs⁺

Be²⁺ > Mg²⁺ > Ca²⁺ > Sr²⁺ > Ba²⁺

Al³⁺ > Mg²⁺ > Na⁺

18.   Order of polarizing power of anions

N^3- > O^2- > F^-

P^3- > S^2- > Cl^-

19.   Chemistry Formula of Bond Order

Bond Order = [N_b-N_a]/2

Where,

                N_a = Number of electrons in antibonding molecular orbitals

                N_b = Number of electrons in bonding molecular orbitals

20.   Some molecules with their bond order, bond length and bond dissociation energy

Molecule	Bond Order	Bond Length (pm)	Bond Dissociation Energy (kJ/mol)
F2	1	142	158
O2	2	121	498
N2	3	110	945

21.   Bond Order in compounds which exhibits Resonance

Bond Order = (Total No. of bonds between two atoms)/(Total No. of resonating structures)

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Empirical relationship between size of nucleus and its mass number is

            R = R₀A^1/3

Where,                       

            R = radius of nucleus,

            A = mass number,

            R₀ = contestant = 1.4x10^-13cm

Rate of Decayof radioactive substance

Where,

            K = decay constant,

            N = No. of atoms,

            t = time of decay,

            dN = small fraction of N,

            dt = small fraction of t

Value of Decay Constant

            

Where,

            N₀ = No. of atoms originally present,

            N = No. of atoms present after time t

Half Life Time (t_1/2)

            t_1/2 = 0.693/K

Where,

            K = decay constant

Average Life Time (T)

            Average life time (T) =Sum of the lives of the nuclei/ Total number of nuclei

            T = 1/K 

Also,

            Average life time (T) = 1.44 x Half-life (T_1/2)

Where,

            K = decay constant

            T = Average Life Time

            T_1/2 = Half Life

Specific Activity

            Specific Activity = Rate of decay/m

                                      = KN/m

                                      = K x Avogadro Number/ Atomic Mass in gram

Where,

            N = Number of Radioactive nuclei that undergoes disintegration

Units of Radioactivity

            Standard unit of radioactivity is curie (c).

            1c = Activity of 1gram Ra²²⁶ = 3.7 x 10¹⁰dps

Where,

            dps = disintegrations per second

millicurie (mc) = 3.7 x 10⁷dps

microcurie (µc) = 3.7 x 10⁴dps

Other units of radioactivity are Rutherford (rd) and Becquerel (Bq).

Rutherford (rd)

1rd = 10⁶dps

Becquerel (Bq)

            Becquerel (Bq) is the SI unit of radioactivity.

                        1Bq = 1 disintegrations per second

                        1 Bq = 1 dps

Radioactive Equilibrium

            A ----à B ----à C

            At steady state,

                        N_A/N_B = K_B/K_A = T_A/T_B

Where,

            K_A = radioactivity constant for the process A---àB

            K_B = radioactivity constant for the process B---àC

            T_A = average life period of A

            T_B = average life period of B

Radioactive Equilibrium in terms of half-life periods,

            N_A/N_B = (T_1/2)A/ (T_1/2)B

Chemistry Formula for Atomic Structure Part 2

Chemistry Formulas for Atomic Structure

Chemistry Formulas from Bohr’s Model of Atom

·         Angular momentum of electron in n^th orbit

Where, m = Mass of the electron,

            v = velocity of electron,

            r = radius of the orbit,

            h = Planck’s constant,

            n = no. of orbit in which electron is present,

·         Energy of electron in n^th orbit

            
           Where, Z = Atomic No. of Electron,

·         Energy absorbed or released in an electron jump ( E)

 

·         Radius of orbits of hydrogen like species

              
         For hydrogen atom Z = 1, for first orbit n = 1,

         On substituting values of the constants

         h = 6.62x10^-27erg sec,

         m = 9.1x10^-28g,

         e = 4.8x10^-10

     we get,

    r = 0.529 Å

So, radius of first orbit of hydrogen atom is 0.529 Å.

·         Radius of n^th orbits of hydrogen like species

r_n = 0.529n²/Z Å

·         Velocity of electron in n^th orbit

          
      On substituting values of the constants

      We get,

·         No. of revolution per second made by an electron around the nucleus of atom

·         Energy of electron in n^th orbit (E_n)

       
        On substituting values of the constants

        We get,          
            

         In general,
                          

·         Energy of electron in a Hydrogen Atom in different energy levels

Energy Level	E (Joules/atom)	E (eV/atom)	E (kcal/mol)
1	-21.79x10-19	-13.6	-313.5
2	-5.42x10-19	-3.4	-78.4
3	-2.41x10-19	-1.51	-38.84
4	-1.36x10-19	-0.85	-19.6
5	-0.87x10-19	-0.544	-12.5
Infinite	0	0	0

·         Frequency or wave length of emitted radiation

          
            Where, λ = wavelength of emitted radiations

                        R = Rydberg constant for Hydrogen atom

·         Number of spectral lines produced when an electron drops from n^th level to ground level

          

Chemistry Formulas from Photoelectric Effect

·         Planck’s Relationship,

E = hv

·         Total energy,

Total Energy = (mv²/2) + w

Where, w = energy required to remove the electron.

Chemistry Formulas from Wave Mechanical Concept of Atom

·         De Broglie’s Equation,

            
          Where, m = mass of particle,

                        v = velocity of the particle,

                        h = Planck’s Constant,

or,       

          

Chemistry Formulas from Heisenberg’s Uncertainty Principle

·        Heisenberg’s Uncertainty Principle,

            
           Where,   = uncertainty in the position of the particle,

                        = uncertainty in the momentum of the particle,

Also,

           

 

Chemistry Formulas from Quantum Numbers

·         Principle Quantum Number (n),

Maximum no. of electrons in n principle quantum number = 2n²

·         Azimuthal Quantum Number (l),

For the given value of principle quantum number (n), azimuthal quantum number (l), may have all integral values from 0 to (n-1)

·         Magnetic Quantum Number (m),

No. of orbitals in a sub-shell = 2 l +1

·         Spin Quantum Number (s),

For spinning of electron about its own axis

Chemistry Formulas for Structure of Atom Part 1