Question:

The process of heating and suddenly cooling of steel is known as :

Updated On: Aug 1, 2022
  • tempering
  • annealing
  • hardening
  • nitriding
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The Correct Option is C

Solution and Explanation

Quenching or hardening is heating up of steel article to redness $(1123\, K)$ and then cooling it suddenly by plunging it in water or oil to make steel hard and brittle Annealing is heating of steel well below red hot and then cooling it suddenly to make it soft. Tempering is heating the quenched steel at around $550\, K$ and then cooling it slowly to make it quite hard but less brittle Nitriding is heating of steel in atmosphere of nitrogen to make its surface hard
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Concepts Used:

d block elements

The elements, in the columns of the periodic table in which d subshells are being occupied are known as d block elements. 

These are the elements that have the capability of forming stable cations with incompletely filled d orbitals. Elements like mercury and Zinc are not considered transition metals because they have electronic configurations: (n-1)d10 ns2. These elements have filled d-orbitals in their ground state and, therefore, even in some of their oxidation states. 

General Properties Of d-Block Elements

  • Multiple oxidation states- The oxidation states of d block elements show very few energy gaps; therefore, they exhibit many oxidation states. Also, the energy difference between s and d orbital is very less. Therefore both the electrons are involved in ionic and covalent bond formation, which ultimately leads to multiple oxidation states.
  • Formation of complex compounds- Ligands show a binding behaviour and can form so many stable complexes with the help of transition metals. This property is mainly due to:
    • Availability of vacant d orbitals.
    • Comparatively small sizes of metals.
  • Hardness- Transition elements are tough and have high densities because of the presence of unpaired electrons.
  • Melting and boiling points- Melting and boiling points of transition are very high. This is because of the presence of unpaired electrons and partially filled d orbitals. Because of these two things, they form strong bonds and therefore have high melting and boiling points.
  • Atomic radii- The atomic and ionic radius of the transition elements decreases as we move from Group 3 to group 6. However, it remains the same between group 7 and group 10, and from group 11 to group 12 increases.
  • Ionization enthalpy- The ionization enthalpies of the transition elements are generally on the greater side as compared to the S block elements