[Xe]4f⁶5d¹6s²,
[Xe]4f⁷5d¹6s² and [Xe]4f⁸5d¹6s²

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

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

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

[Fe(CO)₄]^2$$-$$

[Mn(CO)₆]⁺

Ni(CO)₄

[Co(CO)₄]^$$-$$

the eclipsed conformation of ethane is more stable than staggered conformation even through the eclipsed conformation has torsional strain

the staggered conformation of ethane is more stable than eclipsed conformation, because staggered conformation has no torsional strain

the staggered conformation of ethane is less stable than eclipsed conformation, because staggered conformation has torsional strain

the eclipsed conformation of ethane is more stable than stggered conformation, because eclipsed conformation has no torsional strain.

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

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

Al³⁺ < Mg²⁺ < Na⁺ < F^$$-$$ (increasing ionic size)

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