261.

The first transition element is

• Chromium
• Scandium

• Nickel

• Copper

• Cr³⁺
• Mn³⁺
• Fe³⁺
• Co³⁺
  

The general electronic configuration of transition elements is

• (n – 1)d^1–5
• (n – 1)d^1–10 ns¹
• (n – 1)d^1–10ns^1–2
• None of the above.

The number of d-electrons retained in Fe²⁺ (At. no. of Fe = 26) ion is

• 3

• 4

• 5

• 6

Cr has electronic configuration

• 3s²3p⁶3d⁴4s²
• 3s²3p⁶3d⁵4s¹
• 3s²2p⁶3d⁶ 
• None of the above.

Among the following outermost configurations of transition metals, which show the highest oxidation state?

• 3d³4s²
• 3d⁵4s¹
• 3d⁵4s²
• 3d⁶4s²
  

• 3d⁵4s⁰ 
• 3d⁴4s¹
• 3d³4s²
  
• 3d²4s²p²
  

• MnO₂
• Mn₃O₄
• KMnO₄
• K₂MnO₄
  

Which of the following forms interstitial compounds?

• Fe

• Co

• Ni

• All of the above

Which of the following elements involve gradual filling of 5f level?

• Lanthanides
• Actinides
• Transition metal
• Coinage metals