NCERT Exemplar Class 12 Chemistry Chapter 8 Solutions: The d and f Block Elements
NCERT Exemplar Class 12 Chemistry Solutions Chapter 8 discusses elements that lie in the middle of the periodic table and f block elements’. They are also called the transition elements and this chapter of NCERT Exemplar Class 12 Chemistry clears concepts about their general properties, their electronic configuration, and their variations in ionic and atomic size, oxidation states and ionization enthalpies. You will also learn about some important compounds of these elements, Lanthanides, actinides as well as the application of transition elements. This chapter emphasizes on the first row or 3d elements and their trend in properties.
To solve exemplar problems of NCERT Class 8 Chemistry students must work on the 71 questions given which are spread across 6 sections. The types of questions are varied with MCQs, short and long answer types to matching columns and assertions and reasoning determination.
NCERT Exemplar Problems Class 12 Chemistry is an ideal book to follow for anyone who wants to get good marks in CBSE board as well as in competitive exams. Students, when taking help from Instasolv solutions, get complete guidance on how every answer is derived so that they are better equipped with solving many other similar problems on their own.
Important Topics for NCERT Chemistry Exemplar Solutions Class 12 Chapter 8
- Position of d and f block elements in the periodic table – The elements lying in the group 3 to 11 in the periodic table are called transition and inner transition elements respectively. The d-block of these elements is filled progressively. They are divided into broadly 3 series: 3d-series (Sc – Zn), 4d-series (Y – Cd), and 5-d series (La – Hg except for Ce – Lu). 6d series is still incomplete, it starts with Ac.
- Transition or d block elements – Those elements which have partially filled (n-1) d orbitals in-ground or excited state are called transition elements. They lie in the centre of the periodic table in the range of s-block and p-block. The last electron in these elements usually enters the penultimate or (n-1) d orbitals. They are categorized into 6 series as described below:
- 3d or first transition series – elements having an atomic number between 21-30 and correspond to the filling of 3d shells, e.g.: Sc, Ti, Fe, Cu.
- 4d or second transition series – Elements having an atomic number between 39-48 and correspond to the filling of 4d shells, e.g.: Y, Ag, Cd.
- 5d or third transition series – elements having an atomic number between 72-80 and 57.
- 6d or fourth transition series – Elements having an atomic number between 104-112 and 89.
- Inner transition or f block elements –. The last electron in these elements usually enters the penultimate or (n-2) f orbitals. The last electron in transition elements enters either 4f or 5f orbitals which further divide them into Lanthanides and Actinides.
- Electronic configuration of transition elements – Electronic configuration of an element is defined by the arrangement of electrons in the chief nuclear orbitals which are s, p, d, and f.
- The valence cell configuration of d-block elements is generally given by (n-1) d1-10.ns0,1,2
- The valence cell configuration of d-block elements is generally given by:(n–2) f1-14(n–1) d0-1ns2
- General properties of Transition elements – Due to their identical electronic configuration in the peripheral shell (ns2), all transition elements have similar properties, some of them are:
- they have high boiling and melting points
- they have high density and are hard
- they form coloured compounds and ions
- they form stable complexes
- they can form compounds which are paramagnetic
- Important compounds of transition elements – Transition elements are found in our daily lives in abundance. E.g. Iron is a transition element which is used in cutlery. Some of the compounds of transition elements are:
- Green Vitriol or Ferrous Sulphate – Represented by FeSO4.7H2O it is isomorphous with Epsom salt and effervesces when exposed to air.
- Anhydrous Salt or Ferric Oxide – Represented by Fe2O3 it is yellow in colour and highly soluble in water.
- Calomel or Mercurous Chloride – Represented by Hg2Cl2, it is white in colour and insoluble in water but dissolves in chlorine.
- Lanthanide – In the periodic table, 15 consecutive chemical elements that have atomic numbers between 57 and 71 (from lanthanum to lutetium) are called Lanthanides. Atoms of these elements have similar chemical and physical behaviours.
- Actinides – In the periodic table, 15 consecutive chemical elements that have atomic numbers between 89 and 103 (from actinium to lawrencium) are called Lanthanides. Most of these elements are man-made except a few, like uranium, which is found naturally. Many of the elements in this group are used in atomic weapons owing to their explosive powers
- Few applications of d and f block elements – Since each of the elements in these blocks has a set of specific properties; it makes them useful for many purposes.
- Uses of d block elements:
- Iron and steel are used extensively in the development industry.
- Dry battery cells are made with manganese dioxide.
- Electrical fibres use tungsten
- Silver bromide is used in photography.
- Uses of f block elements:
- Carbides and borides are used in refractories.
- Uranium is used as an atomic fuel
- Thorium finds its use in treating cancer
Discussion of Exercises of NCERT Exemplar Class 12 Chemistry Solutions Chapter 8
- The 1st exercise is MCQ that requires only one correct answer and has 21 questions. They test you on your knowledge of electronic configuration, atomic numbers, metallic radii and density, compounds of transition elements, oxidation state, and actinides.
- The 2nd exercise is MCQ that may have one or more than one correct answer and has 11 questions. They deal with compounds of elements, electronic configuration and properties of these elements, actinides, lanthanides and oxidation states.
- The 3rd exercise requires students to give short answers or explanations and has 20 questions. In this set, students have to apply their expertise on ionization enthalpy, properties and electronic configuration of transition elements, compounds of d and f block elements, the position of elements in the periodic table.
- In the 4th exercise, a table with 2 columns is given and students are required to match elements of the left side with correct ones on the right side. It has 7 questions. The questions revolve around matching catalysts with processes, elements with their uses, properties, oxidation states, and colours.
- The 5th exercise is assertion and reason type questions where a statement is given with a reason and students have to determine the correct combination of answers from the given choices. It has 5 questions which deal with compounds of transition elements, electronic configuration, and oxidation states.
- The 6th exercise requires students to provide longer answers and has 8 questions. It tests you on chemical reactions of transition elements and their compounds, lanthanides and properties of elements in this group, and ionization enthalpy.
- The NCERT Exemplar Class 12 Problems for all chapters of CBSE Class 8 Chemistry is apt for covering the entire syllabus of CBSE boards. The questions make students think on a higher level and they get to practice on many different kinds of question types. By solving these problems one can be sure of being on track with their preparedness for their boards as well as other competitive exams.
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