Explore topic-wise InterviewSolutions in .

A mixture of Tri alkyl aluminium and titanium chloride is called Ziegler – Natta catalyst

E.g. : (C₂H₅)₃ Al + TiCl₄

Elastomers : These are rubber like solids with elastic properties. In elastomers the polymer chains are held together by the weak inter molecular forces.

E.g. : Buna – S, Buna – N etc.

Vitamin C (ascorbic acid) is water soluble. Therefore, it is regularly excreted in urine from the body and cannot be stored.

When the biological response of a drug is therapeutic and useful then the chemical substances (drugs) are called medicines.

Antacids : Chemicals that remove the excess of acid in the stomach and maintain the pH to normal level are antacids.

E.g. : Omeprozole, Lansoprozole etc.,

(1) Ionization energy is the amount of energy required to remove the most loosely held electron from isolated a neutral gaseous atom to convert it into gaseous ion. It is also known as first ionization energy because it is the energy required to remove the first electron from the atom.

It is denoted as I₁ and is expressed in electron volts per atom, kilo calories (or) kilo joules per mole.

M_(g) + I₁ → Mg⁺_(g)  + e^–

I₁ is first ionization potential.

(2) The energy required to remove another electron from the unipositive ion is called the second ionization energy. It is denoted as I₂.

Mg⁺_(g) + I₂ → Mg_(g)²⁺ + e^–

(3) The second ionization potential is greater than the first ionization potential. On removing an electron from an atom, the unipositive ion formed will have more effective nuclear charge than the number of electrons. As a result the effective nuclear charge increases over the outermost electrons. Hence more energy is required to remove the second electron. This shows that the second ionization potential is greater than the first ionization potential.

For sodium, I₁ is 5.1 eV and I₂ is 47.3 eV.

I₁ < I₂ < I₃ .....

In Factors affecting ionization potential :

(1) Atomic radius : As the size of the atom increases the distance between the nucleus and the outermost electrons increases. So the effective nuclear charge on the outermost electrons decreases. In such a case the energy required to remove the electrons also decreases. This shows that with an increase in atomic radius the ionization energy decreases.

(2) Nuclear charge : As the positive charge of the nucleus increases its attraction increases over the electrons. So it becomes more difficult to remove the electrons. This shows that the ionization energy increases as the nuclear charge increases.

(3) Screening effect or shielding effect : In multielectron atoms, valence electrons are attracted by the nucleus as well as repelled by electrons of inner shells. The electrons present in the inner shells screen the electrons present in the outermost orbit from the nucleus. As the number of electrons in the inner orbits increases, the screening effect increases. This reduces the effective nuclear charge over the outermost electrons. It is called screening or shielding effect. With the increase of screening effect the ionization potential decreases. Screening efficiency of the orbitals falls off in the order s > p > d > f.

(Magnitude of screening effect) ∝ 1/(Ionization enthalpy)

Eletronic configurations : Half filled and full filled sub shells are more stable than others. These require more ionisation energy than others.

Niels Bohr quantitatively gave the general features of hydrogen atom structure and it's spectrum. His theory is used to evaluate several points in the atomic structure and spectras.

The postulates of Bohr atomic model for hydrogen as follows 

Postulates :

→ The electron in the hydrogen atom can revolve around the nucleus in a circular path of fixed radius and energy. These paths are called orbits (or) stationary states. These circular orbits are concentric (having same center) around the nucleus.

→ The energy of an electron in the orbit does not change with time.

→ When an electron moves from lower stationary state to higher stationary state absorption of energy takes place.

→ When an electron moves from higher stationary state to lower stationary state emission of energy takes place.

→ When an electronic transition takes place between two stationary states that differ in energy by

∆E is given by ∆E = E₂ – E₁ = hυ

∴ The frequency of radiation absorbed (or) emitted

υ = (E₂ − E₁)/h and E₂ are energies of lower, higher energy states respectively.

→ The angular momentum of an electron is given by mvr = nh/2π

An electron revolve only in the orbits for which it's angular momentum is integral multiple of h/2π.

Limitations :

→ Bohr's theory does not applicable to explain the Multi Electronic Systems Spectra.

→ This theory does not explained the fine structure of hydrogen atom.

→ It does not explained Zeeman effect and Stark effect.