Low melting point of manganese in the 1st transition series is due to:

(a) strong metallic bond due to d¹⁰ configuration

(b) weak metallic bond due to d⁵ configuration

(c) weak metallic bond due to d⁷ configuration

(d) none of the above

CrO₄^2- (yellow) changes to Cr₂O₇^2- (orange) in pH =x and vice versa in pH=y. Hence, x and y are:

1. 6,8

2. 6,5

3. 8,6

4. 7,7

An element that does not show variable oxidation state is:

The pairs having similar magnetic moments are:

The main reason for a larger number of oxidation states exhibited by the actinoids than the corresponding lanthanoids is: 

Correct statement regarding the dichromate ion (Cr₂O₇^2–) is:

1. 4 Cr-O bond lengths are equal.

2. 6 Cr-O bond lengths are equal.

3. All Cr-O bond lengths are equal.

4. None of the Cr-O bond lengths are equal.

Electronic configuration of a transition element X in +3 Oxidation state is [Ar]3d⁵. What is its atomic number?

1. 25

2. 26

3. 27

4. 24

Gadolinium belongs to 4f series. It's atomic number is 64. Which of the following is the correct electronic configuration of gadolinium?

(a) [Xe]4f⁸6d²                    (b) [Xe]4f⁹5s¹

(c) [Xe]4f⁷5d¹6s²                   (d) [Xe]4f⁶5d²6s²

Reason of lanthanoid contraction is

(1) negligible screening effect of 'f orbitals

(2) increasing nuclear charge

(3) decreasing nuclear charge

(4) decreasing screening effect

Which of the following ions will exhibit colour in aqueous solutions ?
(a) La³⁺ (Z=57)
(b) Ti³⁺ (Z=22)
(c) Lu³⁺ (Z=71)
(d) Sc³⁺ (Z=21)