Chemistry Podcast

Sunday, 23 July 2017

What are the factors which favor formation of ionic bonds?

What are the factors which favour formation of Ionic Bonds?

These are the factors which favours formation of ionic bonds...
1. One of the atoms i.e. Metal atom must have low ionization energy, so that it can easily lose its electrons.
2. Other atoms i.e. Non-Metal atoms must have high electron affinity, so that it can hold the extra electrons.
3. One of the atoms i.e. Metal atom should be large in size.
4. Other atoms i.e. Non-Metal atoms should be small in size.
5. Lattice energy of the crystal should be high, means the electrostatic attraction between charged ions in the crystal should be high.
6. Anion and cation should have inert gas electronic configuration
7. The combining elements should differ by at least 1.9 in electronegativity.

Sunday, 16 July 2017

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Chemistry Formulas for Nuclear Chemistry (Radioactivity)

Empirical relationship between size of nucleus and its mass number is
            R = R0A1/3
            R = radius of nucleus,
            A = mass number,
            R0 = contestant = 1.4x10-13cm

Rate of Decayof radioactive substance

            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

            N0 = No. of atoms originally present,
            N = No. of atoms present after time t

Half Life Time (t1/2)

            t1/2 = 0.693/K
            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 
            Average life time (T) = 1.44 x Half-life (T1/2)
            K = decay constant
            T = Average Life Time
            T1/2 = Half Life

Specific Activity

            Specific Activity = Rate of decay/m
                                      = KN/m
                                      = K x Avogadro Number/ Atomic Mass in gram
            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
            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,
                        NA/NB = KB/KA = TA/TB
            KA = radioactivity constant for the process A---àB
            KB = radioactivity constant for the process B---àC
            TA = average life period of A
            TB = average life period of B
Radioactive Equilibrium in terms of half-life periods,
            NA/NB = (T1/2)A/ (T1/2)B

Sunday, 21 May 2017

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 nth 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 nth 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 nth orbits of hydrogen like species

rn = 0.529n2/Z Å

·         Velocity of electron in nth 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 nth orbit (En)

        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)

·         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 nth 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,

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,

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

Sunday, 14 May 2017

Chemistry Formulas for Structure of Atom Part 1

Chemistry Formulas of Structure of Atom

Chemistry Formulas from Rutherford Atomic Model

·         Radius of Nucleus, rn = r0 × A1/3
Where, A = Mass Number,
               r0 = Proportionality Constant = 1.4 × 10-13 cm
·         Volume of the nucleus = Approx. 10-39 cm3
·         Volume of the atom = Approx. 10-24 cm3
·         Density of the nucleus = 1014 g cm-3

Important Characteristics of Three Fundamental Particles
1.      Electron
·         Charge on an Electron = -1.602×10-19 coulombs.
·         Mass of an Electron = 9.11×10-28 g
·         Specific Charge (e/m ratio) of electrons (cathode rays) = 1.76×108 coulombs/gram
·         Radius of the electron = 10-15 cm
·         Density of the electron = 2.17×1017g/cc
·         Mass of one mole of the electrons = Approx. 0.55mg
·         Charge on one mole of the electrons = 96500 Coulombs = 1 Faraday
2.      Proton
·         Mass of Proton = 1.672×10-24g
·         Charge on Proton = 1.602×10-19 Coulombs
·         Specific Charge of Proton = 9.58×104 Coulombs/gram
·         Mass of one mole of proton = 1.007 gram
·         Charge on one mole of proton = 96500 Coulombs = 1 Faraday
·         Volume of Proton = Approx. 1.5×10-38cm3
3.      Neutron
·         Mass of Neutron = 1.675×10-24g
·         Specific Charge on Neutron = 0
·         Density of Neutron = 1.5×1014g/cc
·         Mass of one mole of neutron = 1.008g
4.      Other Sub-Atomic Particles of Atom
·         Positrons
·         Neutrions
·         Mesons
Chemistry Formulas of Atomic Number (Z) and Mass Number (A)
·         General Symbol for an Atom of Element (E) indicating its Atomic Number (Z) and Mass Number (A)
·         Atomic Number (Z) = Number of Protons = Number of Electrons
·         Mass Number (A) = Number of Protons + Number of Neutrons
·         No. of Neutrons = A – Z


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