Transition elements are those elements in which the atoms or ions (in stable oxidation state) contain partially filled d-orbital. These elements lie in the d-block and show a transition of properties between s-block and p-block. Therefore, these are called transition elements.

Elements such as Zn, Cd, and Hg cannot be classified as transition elements because these have completely filled d-subshell.

Transition metal, any of various chemical elements that have valence electrons—i.e., electrons that can participate in the formation of chemical bonds—in two shells instead of only one. While the term transition has no particular chemical significance, it is a convenient name by which to distinguish the similarity of the atomic structures and resulting properties of the elements so designated. They occupy the middle portions of the long periods of the periodic table of elements between the groups on the left-hand side and the groups on the right. Specifically, they form Groups 3 (IIIb) through 12 (IIb). 

Some of the more well-known transitional metals include titanium, iron, manganese, nickel, copper, cobalt, silver, mercury and gold. Three of the most noteworthy elements are iron, cobalt and nickel as they are only elements known to produce a magnetic field.

Heisenberg’s uncertainty principle states that it is impossible to measure or calculate exactly, both the position and the momentum of an object. This principle is based on the wave-particle duality of matter. Although Heisenberg’s uncertainty principle can be ignored in the macroscopic world (the uncertainties in the position and velocity of objects with relatively large masses are negligible), it holds significant value in the quantum world. Since atoms and subatomic particles have very small masses, any increase in the accuracy of their positions will be accompanied by an increase in the uncertainty associated with their velocities.

In the field of quantum mechanics, Heisenberg’s uncertainty principle is a fundamental theory that explains why it is impossible to measure more than one quantum variables simultaneously. Another implication of the uncertainty principle is that it is impossible to accurately measure the energy of a system in some finite amount of time. 

The half-life of a reaction is generally denoted by t1/2. The half-life of reactions depends on the order of reaction and takes different forms for different reaction orders. From the integrated rate equations, concentration of reactants and products at any moment can be determined with the knowledge of time, initial concentration and rate constant of the reaction. Similarly, we can determine time too, with the knowledge of other two variables. The time in which the concentration of the reactant is reduced to one-half of the initial value is known as the half-life of a reaction.

Zero order reaction

In zero order reaction, the rate of reaction depends upon the zeroth power of concentration of reactants. From the integrated rate equation for a zero order reaction with rate constant, k, concentration at any time, t is expressed as,

A → B

[A] = −kt + [A]0

From the definition of half-life of a reaction, at t = t12; [A] = [A]02

⇒ = −kt12 + [A]0

⇒ −kt12 = −[A]02

⇒ t12 = [A]02k

Hence, from the above equation we can conclude that the half life of a zero order reaction depends on initial concentration of reacting species and the rate constant, k. It is directly proportional to initial concentration of the reactant whereas it is inversely proportional to the rate constant, k.

• Transition element:

1. A transition element is defined as the one which has incompletely filled d orbitals in its ground state or in any one of its oxidation states.
2. Zinc, cadmium, mercury are not regarded as transition metals due to completely filled d – orbital.

S-block elements are the elements with valence electrons in the s orbital. Elements in column 1 have one valence electron. Elements in column 2 have two valence electrons. S-block elements are very reactive. Elements in column 1 (the alkali metals) always lose their one valence electron to form a +1 ion. The p-block is the region of the periodic table that includes columns 3A to column 8A and does not include helium. There are 35 p-block elements, all of which are in p orbital with valence electrons. The p-block elements are a group of very diverse elements with a wide range of properties.

1. The electronic configuration for them are ns²np⁶

• Helium 1s ²2s²
• Neon 1s²,2s²,2p⁶
• Argon 1s²,2s²,2p⁶,3s²,3p⁶
• krypton1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p6
• xenon 1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p⁶4d¹⁰5s²5p⁶
• radon 1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p⁶4d¹⁰5s²5p⁶4f¹⁴5d¹⁰6s²6p⁶

2.Atomic size : : It increases down the group as every time a new shell is added as we move down. They actually have Vander wall radii.

1. Ionization energy: They have highest ionization energy due to complete octet.
2. 4. Electron gain Enthalpy: It is positive as they have complete octet so they have no attraction for incoming electron.
3. Melting and boiling point: It is low due to weak force that exists that is Vander wall force.

Down the group size increases therefore Vander wall force also increases so as melting and boiling point increase.

1. All noble gases are odorless and colorless and tasteless.
2. All noble gases are sparingly soluble in water.
3. All are inert gases as they have complete octet.
4. All of them are monatomic.

1. The electronic configuration for them are ns²np⁶

• Helium 1s ²2s²
• Neon 1s²,2s²,2p⁶
• Argon 1s²,2s²,2p⁶,3s²,3p⁶
• krypton1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p6
• xenon 1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p⁶4d¹⁰5s²5p⁶
• radon 1s²,2s²,2p⁶,3s²,3p64s²3d¹⁰4p⁶4d¹⁰5s²5p⁶4f¹⁴5d¹⁰6s²6p⁶

The group 18 elements are helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), and radon (Rn). These elements are non-reactive and are called noble gases as they have their outermost orbit complete. Due to stable electronic configuration they hardly react with other elements.

Preparation of Bleaching Powder

Bleaching powder is synthesized by the action of chlorine gas (produced from the chlor-alkali process) on dry slaked lime (Ca(OH)₂).

Ca(OH)₂ + Cl₂ → CaOCl₂ + H₂O

Uses of Bleaching Powder

• It is used for bleaching dirty clothes in the laundry, as a bleaching agent for cotton and linen in the textile industry.
• It is a strong oxidizing agent, hence used as an oxidizer in many industries.
• It is used as a disinfectant which is used for disinfecting water to make potable water.

Dry slaked lime with reacts with chlorine to prepare bleaching powder.

Cl₂ ​+ Ca(OH)_2​​⟶CaOCl₂​+CaCl₂​+HCl

     Dry slaked lime

The mixture is known as bleaching powder.

Properties of Chlorine:

• It is a greenish yellow gas with pungent and suffocating odour.
• It is soluble in H₂O

The word “electrolysis” was introduced by Michael Faraday in the 19th century. In chemistry, electrolysis is a method that uses a DC to drive a non-spontaneous chemical reaction. This technique is commercially significant as a stage in the separation of elements from naturally occurring sources such as ores using an electrolytic cell.

The process by which ionic substances are decomposed into simpler substances when an electric current is passed through them.

Deacon's process is a process used for preparation of molecular chlorine.

It involves the use of hydrogen chloride and oxygen as reactants and copper chloride as catalyst at high temperatures.

In this process, hydrogen chloride gas is oxidized by atmospheric oxygen in the presence of  CuCl₂ as catalyst at 723 K.

The balanced reaction for deacon's process is written as :

4HCl + O₂ →2Cl₂ + 2 H₂O

The reason F-F bond is weak is that when a fluorine tries to combine with another fluorine atom through a covalent bond, even though it has a very high electronegativity, since fluorine atom has a very small radius the electrons in the atoms repel each other and make the bond weak.

1. Chlorine dioxide is used as oxidizer or disinfectant.

2. Chlorine dioxide is used for control of tastes and odors associated with algae and decaying vegetation.

3. For water treatment, chlorine dioxide has several advantages over chlorine and other disinfectants.

According to Ellingham diagram the lower the position of a metal line in the Ellingham diagram, the greater is the stability of its oxide i.e lower metal line will have most negative Gibbs free energy due to which metal will be most stable in the form of its oxide. Bromine being in between lacks both these characteristics. Thus, the stability of oxides of halogens decreases in the order : I > Cl > Br > F. Higher oxide halogens are more stable than the lower ones because the higher ones are less reactive than the lower ones and also the size of the atoms are more of higher so they are less reactive and hence the oxides are more stable.

Uses of Interhalogen Compounds

• These are used as non-aqueous solvents.
• They are used as a catalyst in few reactions.
• UF₆ which is used in the enrichment of ²³⁵ U is produced by using ClF₃ and BrF₃.

U (s) + 3ClF₃ (l) → UF₆ (g) + 3ClF (g)

• These are used as fluorinating compounds.

While both Oxygen and Chlorine are chemically-active, they cannot form compounds with the inert gasses, while Fluorine is the most chemically-active of all the elements. Elements grouped together on the periodic table have similar electron configurations and therefore similar chemical properties and reactivity.

Oxygen fluorides are compounds of elements oxygen and fluorine with the general formula OnF2, where n = 1 to 6. Many different oxygen fluorides are known:

oxygen difluoride (OF2)
dioxygen difluoride (O2F2)
trioxygen difluoride or ozone difluoride (O3F2)[1][2]
tetraoxygen difluoride (O4F2)[3]
pentaoxygen difluoride (O5F2)
hexaoxygen difluoride (O6F2)[4]
dioxygen monofluoride(O2F)

tetraoxygen difluoride
Oxygen fluorides are strong oxidizing agents with high energy and can release their energy either instantaneously or at a controlled rate. Thus, these compounds attracted much attention as potential fuels in jet propulsion systems.