Question 1

Which of the following prediction is correct when the transition metal ion is colourless?

Accepted Answer

The colour of transition metal ions is primarily due to d-d transitions, which require the presence of partially filled d-orbitals. When the d-orbitals are completely empty (d^0 configuration, e.g., Sc^ 3+ , Ti^ 4+ ) or completely filled (d^ 10 configuration, e.g., Zn^ 2+ , Cu^+), d-d transitions are not possible. In both d^0 and d^ 10 configurations, there are no unpaired electrons. Therefore, a transition metal ion is colourless when it contains 0 unpaired electrons. Answer: it contains 0 unpa

Question 2

Which of the following pairs of elements does NOT include transition elements?

Accepted Answer

Transition elements are the d-block elements (groups 3 to 12) in the periodic table, which have incompletely filled d-orbitals in their ground state or in any of their common oxidation states. Mn (Manganese, Group 7) and Ag (Silver, Group 11) are transition elements. Zr (Zirconium, Group 4) and Au (Gold, Group 11) are transition elements. Mo (Molybdenum, Group 6) and Pt (Platinum, Group 10) are transition elements. Sn (Tin) belongs to Group 14 and is a p-block element. Pm (Promethium) is a lanth

Question 3

Identify the catalyst used in synthesis of gasoline by Fischer Tropsch process.

Accepted Answer

The Fischer-Tropsch process is a collection of chemical reactions that converts a mixture of carbon monoxide and hydrogen (syngas) into liquid hydrocarbons, such as gasoline. The reaction requires a catalyst to proceed efficiently. The most common and historically significant catalysts used for this synthesis are based on transition metals like cobalt, iron, or ruthenium. Specifically, a mixture of cobalt and thorium oxide (Co-Th) supported on kieselguhr is a classic and widely used catalyst in

Question 4

Which element from following has highest melting point?

Accepted Answer

The melting point of transition metals depends on the strength of metallic bonding, which is directly proportional to the number of unpaired electrons available for bonding. The electronic configurations of the given elements are: V : [ Ar ] 3d^3 4s^2 (3 unpaired electrons) Cr : [ Ar ] 3d^5 4s^1 (6 unpaired electrons) Mn : [ Ar ] 3d^5 4s^2 (5 unpaired electrons) Fe : [ Ar ] 3d^6 4s^2 (4 unpaired electrons) Chromium (Cr) has the maximum number of unpaired electrons (6), which leads to the stronge

Question 5

Which element from following is NOT regarded as transition element ?

Accepted Answer

A transition element is defined as an element that has an incompletely filled d-orbital in its ground state or in any of its common oxidation states. Cadmium ( Cd ) belongs to group 12 and has the ground state electronic configuration [ Kr ] 4d^ 10 5s^ 2 . In its common oxidation state of +2, its configuration is [ Kr ] 4d^ 10 . Since the d-orbitals are completely filled in both its ground state and its stable oxidation state, Cd is not regarded as a transition element. Copper ( Cu ) and Gold (

Question 6

Identify species having metal atom in +6 oxidation state from following

Accepted Answer

Let x be the oxidation state of the metal atom in each species. For MnO _4^-, the oxidation state of Mn is calculated as: x + 4(-2) = -1 x = +7 For [ Cr ( CN )_6]^ 3- , the oxidation state of Cr is calculated as: x + 6(-1) = -3 x = +3 For Cr _2 O _3, the oxidation state of Cr is calculated as: 2x + 3(-2) = 0 x = +3 For CrO _2 Cl _2, the oxidation state of Cr is calculated as: x + 2(-2) + 2(-1) = 0 x - 6 = 0 x = +6 Thus, CrO _2 Cl _2 has the metal atom in the +6 oxidation state. Answer: CrO _2 Cl

Question 7

Which from following is NOT an inner transition element ?

Accepted Answer

Inner transition elements are the f-block elements, which include the lanthanides (atomic numbers 58 to 71) and actinides (atomic numbers 90 to 103). Sometimes, Lanthanum (Z=57) and Actinium (Z=89) are also studied along with them due to their similar properties. Ho (Holmium, Z=67) and Lu (Lutetium, Z=71) belong to the lanthanide series. Ac (Actinium, Z=89) is the prototype of the actinide series. Rf (Rutherfordium, Z=104) is a transactinide element. It belongs to Group 4 and Period 7 of the per

Question 8

What is the highest possible oxidation state exhibited by manganese ?

Accepted Answer

The atomic number of manganese (Mn) is 25. Its electronic configuration is [Ar] 3d^ 5 4s^ 2 . The highest oxidation state is achieved when all the valence electrons (both 4s and 3d electrons) participate in bonding. Total number of valence electrons = 5 + 2 = 7. Therefore, the highest possible oxidation state exhibited by manganese is +7, which is seen in compounds like KMnO_ 4 and Mn_ 2 O_ 7 . Answer: +7

Question 9

Identify metals present in brass.

Accepted Answer

Brass is an alloy composed primarily of copper (Cu) and zinc (Zn). The proportions of copper and zinc can be varied to create a range of brasses with varying properties. Answer: Cu and Zn

Question 10

Identify general electronic configuration exhibited by 2^ nd series of transition elements.

Accepted Answer

The second series of transition elements is the 4d series, which starts from Yttrium (Z=39) and ends at Cadmium (Z=48). The noble gas preceding this series is Krypton ([ Kr ], Z=36). The valence electrons are filled in the 4d and 5s subshells. Due to anomalous configurations (for example, Palladium has the configuration [ Kr ]\ 4d^ 10 \ 5s^0 and elements like Silver have [ Kr ]\ 4d^ 10 \ 5s^1), the number of electrons in the 5s orbital can be 0, 1, or 2. Thus, the general electronic configuratio

Question 11

Which lanthanoid from following exhibits f^ 14 configuration in +3 state?

Accepted Answer

The electronic configuration of Lutetium (Lu), which has an atomic number of 71, is [ Xe ] 4f^ 14 5d^ 1 6s^ 2 . In the +3 oxidation state, Lu loses two electrons from the 6s orbital and one electron from the 5d orbital. Therefore, the electronic configuration of Lu ^ 3+ is [ Xe ] 4f^ 14 . For the other given elements in their +3 state: Tm ^ 3+ (Z=69) has the configuration [ Xe ] 4f^ 12 . Ce ^ 3+ (Z=58) has the configuration [ Xe ] 4f^ 1 . Dy ^ 3+ (Z=66) has the configuration [ Xe ] 4f^ 9 . Answe

Question 12

Which from following pair of elements in their respective oxidation states have same number of unpaired electrons ?

Accepted Answer

The electronic configuration of Fe (Z=26) is [ Ar ] 3d^6 4s^2. The electronic configuration of Fe ^ 2+ is [ Ar ] 3d^6. It has 4 unpaired electrons. The electronic configuration of Mn (Z=25) is [ Ar ] 3d^5 4s^2. The electronic configuration of Mn ^ 2+ is [ Ar ] 3d^5. It has 5 unpaired electrons. The electronic configuration of Co (Z=27) is [ Ar ] 3d^7 4s^2. The electronic configuration of Co ^ 2+ is [ Ar ] 3d^7. It has 3 unpaired electrons. The electronic configuration of Ni (Z=28) is [ Ar ] 3d^8

Question 13

What is the total number of transition series of d-block elements?

Accepted Answer

The d-block elements are distributed into four transition series based on the filling of d-orbitals: First transition series (3d series): Sc (Z=21) to Zn (Z=30) Second transition series (4d series): Y (Z=39) to Cd (Z=48) Third transition series (5d series): La (Z=57), Hf (Z=72) to Hg (Z=80) Fourth transition series (6d series): Ac (Z=89), Rf (Z=104) to Cn (Z=112) Therefore, there are a total of 4 transition series of d-block elements. Answer: 4

Question 14

Which actinoid from following has smallest ionic size in +3 state?

Accepted Answer

In the actinoid series, as the atomic number increases from Actinium (Ac) to Lawrencium (Lr), there is a gradual decrease in the size of atoms or M^ 3+ ions. This phenomenon is known as actinoid contraction, which is due to the poor shielding effect of the 5f electrons. The given elements belong to the actinoid series with the following atomic numbers: Pa (Z = 91) Cm (Z = 96) Fm (Z = 100) Lr (Z = 103) Since Lawrencium (Lr) has the highest atomic number among the given options, it experiences the

Question 15

What is the atomic number of first post actinoid element ?

Accepted Answer

The actinoid series consists of elements with atomic numbers from 90 to 103. The elements that follow the actinoid series are known as post-actinoid elements. Therefore, the first post-actinoid element has an atomic number of 104, which is Rutherfordium (Rf). Answer: 104

Question 16

Which from following pair of elements in their respective oxidation states develops same value of calculated spin only magnetic moment ?

Accepted Answer

The spin-only magnetic moment is given by = n(n+2) BM, where n is the number of unpaired electrons. Electronic configuration of Ti ^ 3+ is [ Ar ] 3d^ 1 , so n = 1. Electronic configuration of Zn ^ 2+ is [ Ar ] 3d^ 10 , so n = 0. Electronic configuration of Cr ^ 2+ is [ Ar ] 3d^ 4 , so n = 4. Electronic configuration of Fe ^ 2+ is [ Ar ] 3d^ 6 , so n = 4. Electronic configuration of Cr ^ 3+ is [ Ar ] 3d^ 3 , so n = 3. Electronic configuration of Cu ^ 2+ is [ Ar ] 3d^ 9 , so n = 1. Since both Cr ^

Question 17

Why transition elements have more tendency to form interstitial compounds?

Accepted Answer

Transition metals crystallize in close-packed structures such as hcp, ccp, or bcc. These crystal lattices contain empty spaces or voids known as interstitial sites. Small non-metallic atoms like hydrogen, carbon, nitrogen, and boron can easily occupy these interstitial sites without significantly distorting the original crystal lattice. Due to the presence of these interstitial sites (voids) in their crystal lattice, transition elements have a high tendency to form interstitial compounds. Answer

Question 18

Which of the following series of transition elements has general electronic configuration, [ Kr ]\,4d^ 1-10 \,5s^ 0-2 ?

Accepted Answer

The general electronic configuration [ Kr ]\,4d^ 1-10 \,5s^ 0-2 corresponds to the transition elements of the 5th period. In these elements, the 4d subshell is progressively filled from Yttrium (Y) to Cadmium (Cd). Since the 4d orbitals are being filled, this series is known as the 4d series of transition elements. Answer: 4d series elements

Question 19

What is the oxidation state of chromium in the final product when KI reacts with acidified potassium dichromate solution?

Accepted Answer

Potassium dichromate (K_2Cr_2O_7) acts as a strong oxidizing agent in an acidic medium. It oxidizes iodide ions (I^-) from KI to iodine (I_2) and itself gets reduced to chromium(III) ions (Cr^ 3+ ). The ionic equation for the reaction is: Cr_2O_7^ 2- + 14H^+ + 6I^- 2Cr^ 3+ + 3I_2 + 7H_2O In the final product, chromium is present as Cr^ 3+ . Therefore, the oxidation state of chromium in the final product is +3. Answer: +3

Question 20

Identify the factor responsible for colour of transition metal compounds.

Accepted Answer

The colour of transition metal compounds is primarily due to d-d transitions. In transition metal complexes, the five degenerate d-orbitals split into two sets of different energies (e.g., t_ 2g and e_g in an octahedral field) due to the presence of ligands. When white light falls on the complex, an electron from a lower energy d-orbital absorbs a specific wavelength of light and gets excited to a higher energy d-orbital. The transmitted or reflected light, which is complementary to the absorbed

d and f Block Elements — Previous Year Questions & Solutions