General trends - size, ionisation enthalpy, oxidation states, colour and catalysis — NEET & JEE Questions

Question 1 · difficulty L1 · recall

A characteristic feature of transition elements is that they often show

• A. variable oxidation states
• B. only the +1 oxidation state
• C. only colourless ions
• D. no catalytic activity

Question 2 · difficulty L2 · understanding

Across the first transition series, atomic radii generally

• A. increase sharply from Sc to Zn
• B. decrease slightly and then remain nearly constant
• C. remain exactly constant
• D. double from Sc to Zn

Question 3 · difficulty L2 · understanding

Why do many transition-metal ions appear coloured?

• A. Electronic transitions can occur between split d-orbitals
• B. All transition ions emit visible light spontaneously
• C. Their nuclei absorb visible light
• D. Every coloured ion must contain an unpaired s electron

Question 4 · difficulty L2 · understanding

Why are transition metals often good catalysts?

• A. They can show variable oxidation states and provide surfaces for adsorption
• B. They are always gases
• C. They have no d electrons
• D. They never form intermediate compounds

Question 5 · difficulty L3 · application

Which ion is expected to be colourless because it has a $d^0$ configuration?

• A. $Ti^{4+}$
• B. $Ti^{3+}$
• C. $V^{2+}$
• D. $Mn^{2+}$

Question 6 · difficulty L3 · application

Which ion is most likely to be colourless because it has a $d^{10}$ configuration?

• A. $Cu^+$
• B. $Cu^{2+}$
• C. $Fe^{3+}$
• D. $Co^{2+}$

Question 7 · difficulty L3 · application

Which element in the first transition series commonly shows the highest oxidation state?

• A. Sc
• B. Ti
• C. Mn
• D. Zn

Question 8 · difficulty L3 · application

Which statement best explains why $Fe^{2+}$ and $Fe^{3+}$ are both common?

• A. The energies of 4s and 3d electrons are comparable, allowing different numbers of electrons to participate in oxidation
• B. Iron has no d electrons
• C. Iron can lose only core electrons
• D. Both ions have identical electron configurations

Question 9 · difficulty L4 · application

Which trend is most reasonable for the first ionisation enthalpies across the first transition series?

• A. They show an overall gradual increase with irregularities
• B. They decrease smoothly from Sc to Zn
• C. They remain exactly constant
• D. They alternate between zero and very large values

Question 10 · difficulty L4 · application

A transition-metal ion is intensely coloured and also changes oxidation state readily in reactions. Which two properties of transition elements are being illustrated?

• A. d-electron transitions and variable oxidation states
• B. large atomic size and low density
• C. absence of d electrons and fixed valency
• D. complete chemical inertness and diamagnetism