General electronic configuration of d - block elements is

In first transition series which of the following has lowest enthalpy of atomisation ?

Which of the following ion is colourless in aqueous solution ?

In the reaction : \(NaCI+{ K }_{ 2 }{ Cr }_{ 2 }{ O }_{ 7 }+conc.{ H }_{ 2 }{ SO }_{ 4 }\underrightarrow { heat } X+{ Na }_{ 2 }{ SO }_{ 4 }+{ K }_{ 2 }{ SO }_{ 4 }+{ H }_{ 2 },X\) is a raddish brown gas which gives a yellow solution on passing through water and a yellow precipitate on treating the solution with lead acetate solution X could be

Which is the strongest base among the following ?

KMnO₄ acts as an oxidising agent in acidic medium. The number of moles of KMnO₄ that will be needed to react with one mole of sulphide ions in acidic solution is

What is meant by 'lanthanoid contraction'?

Name a transition element which does not exhibit variable oxidation states.

Reactivity of transition elements decreases almost regularly from Sc to Cu. Explain.

Transition metals in which vacant spaces are occupied by small atoms such as hydrogen, carbon etc. are called _____________________.

Which of the 3d series of the transition metals exhibits the largest number of oxidation states and why?

Assign reasons for the following:
(i) Copper (I) ion is not known in aqueous solution.
(ii) Actinoids exhibit greater range of oxidation states than lanthanoids.

In what way is the electronic configuration of the transition elements different from that of the non transition elements?

Give reasons for the following : Variations in the radii of transition elements are not as pronounced as those of representative elements.

Explain why mercury (I) ion exists as \({ Hg }_{ 2 }^{ 2+ }\) ion while copper (I) ion exists as Cu⁺ ion.

(a) Comlete the following chemical equations for reactions in aqueous media:
(i) Cr₂O₇^2-+H⁺+Fe2+ \(\longrightarrow \)
(ii) MnO₄^-+I^-+H⁺\(\longrightarrow \)
(b) How many unpaired electrons are present in Mn²⁺ ion (At. no. of Mn =25)? How does it influence magnetic behaviour of Mn²⁺ ions?

Why do the transition elements exhibit higher enthalpies of atomisation?

Explain why a green solution of potassium manganate turns purple and a brown solid is precipitated when \({ CO }_{ 2 }\)gas is bubbled into the solution ?

Describe the preparation of potassium permanganate from pyrolusite ore. Write the ionic equation for the reaction that takes place between acidified KMnO₄ solution and iron (II) ions

Compare the chemistry of the actinoids with that of lanthanoids with reference to the following :
(i) Electronic configuration
(ii) Oxidation states
(iii) Chemical reactivity

(a) Write the electronic configuration of Ce³⁺ ion, and calculate the magnetic moment on the basis of 'spin-only' formula. [Atomic No. of Ce = 58]
(b) Account for the following
(i) The enthalpies of atomisation of the transition metals are high.
(ii) The lowest oxide of a transition metal is basic, the highest is amphoteric/ acidic.
(iii) Cobalt (II) is stable in aqueous solution but in the presence of complexing agents, it is easily oxidised. 

The chemistry of the actinoid elements is not so smooth as that of the lanthanoids. Justify this statement by giving some examples from the oxidation state of these elements.

Account for the following :
(a) Transition metals show variable oxidation states.
(b) Zn, Cd and Hg are soft metals
(c) E^o value for the Mn³⁺ /Mn²⁺ couple is highly positive (+ 1.57 V) as compared to Cr³⁺ /Cr²⁺.
(ii) Write one similarity and one difference between the chemistry of lanthanoid and actinoid elements.