The electronic configuration of Eu (Atomic no.63), Gd (Atomic no. 64) and Tb (Atomic no. 65) are

• [Xe]4f⁶ 5d¹ 6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹  6s² 

• [Xe] 4f⁶ 5d¹ 6s² , [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁸ 5d¹ 6s² 

• [Xe] 4f⁷  6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s² 

• [Xe] 4f⁷  6s², [Xe] 4f⁷ 5d¹ 6s² and [Xe] 4f⁹ 6s² 

In which of the following options the order of arrangement does not agree with the variation of the property indicated against it?

• B<C<N<O (increasing first ionisation enthalpy)

• I<Br<Cl<F(increasing electron gain enthalpy)

• Li<Na<K<Rb (increasing metallic radius)

• Li<Na<K<Rb (increasing metallic radius)

The species Ar, K⁺ and Ca²⁺ contain the same number of electrons. In which order do their radii increase?

• Ar < K⁺< Ca²⁺

• Ca²⁺ < Ar < K⁺

• Ca²⁺ < K⁺ < Ar

• Ca²⁺ < K⁺ < Ar

Solubility of the alkaline earth's metal sulphates in water decreases in the sequence

• Mg>Ca>Sr>Ba

• Ca>Sr>Ba>Mg>

• Sr>Ca>Mg>Ba

• Sr>Ca>Mg>Ba

5.

Which of the following pairs of ions are isoelectronic and isostructural? 

• 
• 
• 
• 

The number of d- electrons in Fe²⁺ (Z = 26) is not equal to the number of electrons in which one of the following?

• S- electronic in Mg (Z=12)

• p-electrons in Cl( Z=17)

• d- electrons in Fe (Z=26)

• d- electrons in Fe (Z=26)

which of the following orders of ionic radii is correctly represented?

• H^- > H >H⁺

• Na⁺ >F^- >O^2-

• F^- > O^2->Na⁺

• F^- > O^2->Na⁺

Be²⁺ is isoelectronic with which of the following ions?

• H⁺

• Li⁺

• Na⁺

• Na⁺

Identify the wrong statement in the following.

• Amongst isoelectronic species, smaller the positive charge on the cation, smaller is the ionic radius

• Amongst isoelectronic species, greater the negative charge on the anion, larger is the ionic radius

• Atomic radius of the elements increases as one moves down the first group of the periodic table

• Atomic radius of the elements increases as one moves down the first group of the periodic table

Which of the following represents the correct order of increasing electron gain enthalpy with negative sign for the elements O, S, F and Cl?

• Cl < F < O < S

• O < S < F< Cl

• F < S < O < Cl

• F < S < O < Cl