Explore topic-wise InterviewSolutions in .

The correct choice is (b) False

The BEST I can explain: The highest oxidation state in the oxides of any transition METAL is equal to its group number, for example, 7 in Mn2O7. Beyond group 7, no HIGHER oxides of iron above Fe2O3 are known. Some metals in higher oxidation state STABILIZE by forming oxocations.

The correct CHOICE is (c) Zn

Best explanation: All transition elements are d-block elements, but all d-block elements are not transition elements. ZINC has the electronic CONFIGURATION [Ar] 3d^104s^2, and the configuration of the Zn^2+ ION is [Ar] 3d^10. THUS, both the element and its only known stable ion have completely filled d-orbitals. Also, the metal does not exhibit any variable valency or multiple oxidation states in compound formation.

The correct answer is (C) Magnetic

For explanation: Their magnetic PROPERTIES cannot be explained EASILY, as they are more complex. The 5f bands FORMED due to 5f-5f wave function overlap or to hybridisation with s, p or d electrons. As a RESULT of the band formation, a wide variety of magnetic phenomena may occur.

Correct ANSWER is (a) Lu^+3 and Ln^+3

For explanation: Many trivalent lanthanide ions are COLORED both in the solid state and in aqueous state due to f-f ELECTRONIC transition. Lu^+3 and Ln^+3 don’t exhibit color due to absence of UNPAIRED electrons. All lanthanide ions except La^+3, Ce^+3 and Lu^+3 are paramagnetic due to PRESENCE of unpaired electrons.

Correct choice is (a) (n-1)d^1-10ns^0-2

Easiest explanation: D-block elements are so-called since, in them, 3d, 4d, 5d and 6d subshells are incomplete and the last electron ENTERS the (n-1)d orbital, i.e., penultimate (last but ONE) shell. Their GENERAL ELECTRONIC configuration is (n-1)d^1-10ns^0-2, where n is the outermost shell.

Right choice is (d) Zinc

The BEST explanation: Ionisation enthalpy shows only a little variation on moving ALONG the PERIOD of d-block elements. The first ionisation enthalpy of zinc, cadmium and MERCURY are higher than the other elements in their respective PERIODS because of the fully filled (n-1)d^10ns^2 configuration.

Right answer is (c) D-block elements show irregular and erratic chemical properties

For explanation I WOULD say: There is very little variance in the atomic size of the ACTINOIDS and so, they show similar properties. 4f and 5f orbitals belong to different ENERGY levels and so are UNEQUALLY shielded. The same applies to the 4d and 5d orbitals. The d-block elements are known to show irregular and erratic chemical properties.

The CORRECT option is (a) Metallic

The best EXPLANATION: Because they are all metals, the transition elements are often CALLED the transition metals. As a group, they DISPLAY typical metallic properties and are less reactive than the metals in group 1 and group 2 of the PERIODIC table.

Right CHOICE is (c) Lanthanoid contraction

The explanation: In the atoms of the second transition series, the number of shells INCREASES and so, their atomic RADII is greater than that of the FIRST transition series. The atomic radii of the second and third transition series are almost same due to lanthanoid contraction.

Correct OPTION is (d) The melting point of the metal ranges from 500-1000K

Easiest explanation: All lanthanides are soft metals with SILVERY white color. They tarnish rapidly by air. With INCREASE in atomic number, the harness of these metals also INCREASES. The melting points of the lanthanides ranges from 1000 to 1200K but SAMARIUM melts at 1623K.

The correct answer is (C) Actinium

Easy explanation: The fourth transition SERIES or 6d series CORRESPONDING to the filling of 6d SUBLEVEL starts with Actinium (Atomic No. = 89) followed by elements with atomic number 104 onwards. These elements lie in the seventh period of the periodic table.

Correct answer is (a) Chromyl CHLORIDE test

The explanation: Chromyl chloride test is done for detecting the presence of Cl^– ions. The chlorides of silver, lead, mercury and antimony are covalent in NATURE and thus do not GENERATE Cl^– ions and so they do not give the chromyl chloride test also. So, HEAVY metal chlorides don’t give this test because they are not ionic.

Correct choice is (b) +3

Easiest explanation: The properties of SCANDIUM compounds are intermediate between those of aluminium and yttrium. A diagonal relationship EXISTS between the behaviour of MAGNESIUM and scandium, just as there is between beryllium and aluminium. In the chemical compounds of the elements in group 3, the PREDOMINANT oxidation STATE is +3.

Correct answer is (B) P-239

To ELABORATE: The most common plutonium isotope formed in a typical nuclear REACTOR is the fissile Pu-239, formed by neutron capture from U-238 (followed by BETA decay), and which when fissioned yields much the same energy as the fission of U-235.

Right choice is (c) Fe2O3

Best EXPLANATION: Ferric oxide(Fe2O3) occurs in nature as haematite. It is a red powder, INSOLUBLE in H2O and not acted upon by air or H2O. It is AMPHOTERIC in nature and reacts with acids and alkalis and used as a catalyst in the oxidation of CO to CO2 in the Bosch PROCESS.

Right CHOICE is (a) V

The best I can explain: The first transition SERIES or 3d series corresponding to the filling of 3d sublevel consists of the following 10 elements of the 4^th period: Sc (Atomic No. = 21), TI, V, CR, Mn, Fe, CO, Ni, Cu and Zn (Atomic No. = 30).

Right OPTION is (b) The radius decreases

To explain: The gradual decrease in the atomic and ionic radii of the lanthanides with an increase in atomic number is CALLED lanthanide CONTRACTION. It OCCURS due to the poor shielding effect of the 4f electrons.

Right answer is (d) Metallic bond

To elaborate: Transition elements have relatively low ionization ENERGIES and have one or two electrons in their outermost energy level. As a result, they form metallic bonds. This is ALSO the REASON BEHIND the metallic PROPERTIES of transition elements.

The correct choice is (a) True

Easy explanation: In the BEGINNING of the series, the atomic radius decreases with increase in atomic number as the NUCLEAR charge increases and the SHIELDING effect of the d-electrons is small. After midway, the INCREASED number of d-electrons show an increase in shielding effect which counterbalances the increase in nuclear charge. Therefore, the decrease in atomic radius post midway is MINIMAL.

Right choice is (b) Zinc

For explanation: Zinc has no UNPAIRED ELECTRONS in its d orbital and has a stable FULLY filled d orbital. Hence, due to the absence of unpaired electrons in Zinc, it can show no specific colouration in its salts. All salts and solutions of Zinc are always WHITE due to this fact.

Correct answer is (b) Chromium

The explanation: Chrome plating (less commonly chromium plating), often REFERRED to simply as chrome, is a technique of electroplating a thin layer of chromium ONTO a metal object. The chromed layer can be decorative, PROVIDE corrosion resistance, EASE cleaning PROCEDURES, or increase surface hardness.

Right answer is (c) K2CR2O7

To explain: POTASSIUM DICHROMATE (K2Cr2O7) is especially useful in the visible range but also useful in UV. Potassium dichromate itself is stable and available in high purity. In dilute perchloric acid SOLUTION, it has a linear response with good temperature stability and also stable as solution.

Correct choice is (B) False

Easy explanation: Lanthanide contraction is the steady decrease in the size of the atoms with increasing atomic number from lanthanum (atomic number 57) through lutetium (atomic number 71). The Lanthanide Contraction is CAUSED by a POOR shielding EFFECT of the 4f electrons. It’s due to lanthanide contraction, as the atomic number increases, the size of the lanthanide atoms and their tripositive ions decreases.

Right option is (b) (n-1)d

Explanation: In these ELEMENTS, the last ELECTRON ENTERS the d orbital of the penultimate SHELL, i.e., the last electron goes to (n-1) d orbital. Hence, these elements are named as d-block elements. These elements have PARTLY filled d-subshells in their elementary form or in their simple ions.

The correct choice is (a) Hydrochloric acid

To ELABORATE: Actinoids are highly REACTIVE metals ESPECIALLY in the finely divided state. All these metals are attacked by hydrochloric acid but the effect of nitric acid is very SMALL due to the formation of a PROTECTIVE oxide layer on their surface.

Right choice is (a) True

Best EXPLANATION: Lanthanoids are INVOLVED in the filling of 4F- orbitals, whereas actinoids are involved in the filling of 5f-orbitals. The binding energy of 4f electrons is comparatively less than that of 5f-electrons. The COMPOUNDS FORMED by lanthanides are less basic, whereas the compounds of actinides are highly basic.

The correct CHOICE is (c) Mercury

Best explanation: Mercury (atomic no.80, symbol-Hg) is the only liquid metal at ROOM temperature. It has a high coefficient of expansion and boiling point. This HELPS us to identify even the SLIGHTEST change in temperature of the SURROUNDINGS.

Right option is (d) LANTHANUM

To elaborate: In the periodic table, when you move down the group, the atomic number increases. In the GIVEN OPTIONS, scandium and titanium belong to the 3d SERIES, cadmium belongs to the 4d series and Lanthanum belongs to the 5d series. Therefore, Lanthanum will have the highest atomic number.

The CORRECT option is (b) Cr2O3

Best explanation: CHROMIUM(atomic no.24, symbol-Cr) forms many OXIDES. Some of its common oxidation states are +2, +3 and +6. Chromium (III) OXIDE (green in colour) is amphoteric, i.e., it can react as both acid and BASE. Its formula is Cr2O3.

The correct choice is (c) Uranium

The explanation is: Uranium is used as fuel in nuclear reactors. Itis mined and goes through REFINING and enrichment before being LOADED into a nuclear reactor. Nuclear power PLANTS use a certain kind of uranium, referred to as U-235, for fuel because its ATOMS are easily split apart.

Correct choice is (a) La, Ce, Pr, Nd, Pm

To elaborate: The first FIVE elements of Lanthanides are:

LANTHANUM (La) – 57

Cerium (Ce) – 58

Praseodymium (Pr) – 59

Neodymium (Nd) – 60

Promethium (Pm) – 61.

Right option is (c) Zn, CD, Hg

To explain I would say: Transition elements refer to those d-block elements who have their PENULTIMATE shells incomplete. In the CASE of Zinc, cadmium and mercury, since their penultimate shell is completely occupied, they are referred to as d-block elements and not REGARDED as transition elements.

Right ANSWER is (a) True

The EXPLANATION is: The STUDY of transition elements is IMPORTANT because precious metals such as silver, GOLD and platinum as well as industrially important metals such as iron, copper and titanium are transition elements.

The CORRECT answer is (d) THORIUM

To explain: Thorium (ATOMIC no.90, symbol-Th) is used in atomic reactors and in the treatment of cancer. Its salts are used in making incandescent gas MANTLES. Thorium is formed by the radioactive of uranium and is used to treat tumours.

Correct CHOICE is (d) +3

To explain I would say: The most common and stable OXIDATION state of lanthanides is +3. Some elements also EXHIBIT +4 oxidation states. Some elements exhibit +2 oxidation state also due to their half-filled, fully-filled and noble GAS configuration.

Right OPTION is (B) Purple

The best I can explain: The physical state of potassium PERMANGANATE (KMnO4) is an odourless SOLID, and they LOOK like dark purple or bronze-coloured crystals. If we dissolve these crystals in water, then the solution becomes purple in colour.

Right option is (a) True

For explanation: Iron and TITANIUM are the most abundantly found transition elements. The most abundant transition metal in EARTH’s SOLID crust is iron, which is fourth AMONG all elements and second (to aluminum) among metals in crustal abundance.

Correct answer is (d) Uranium

To explain I WOULD say: Uranium (atomic no. 92, symbol-U) is used as nuclear fuel. Its salts are used in the glass industry (for imparting green COLOUR), textile industry, ceramic industry and in MEDICINES. Natural uranium has three major isotopes.

Correct option is (a) True

Easy explanation: In lanthanides, Ce changes from +4 to +3 oxidation state. Formation of Ce^4+ is favorable DUE to its NOBLE GAS configuration. HOWEVER, Ce^+4 changes to Ce^+3 as it is a strong oxidizing agent. The E° value of Ce^+4/Ce^+3 is +1.74 V.

The correct answer is (b) Transition elements have low ENTHALPIES of atomisation

Explanation: Transition metals generally have high melting and BOILING points. Magnesium and technetium have abnormally low boiling points. This is due to the STRONG METALLIC BONDS between the atoms. They have high enthalpies of atomization.