Transition Metals' Shared Properties

Steps:

• Locate vanadium (atomic number 23), chromium (24), and cobalt (27) in the d-block of the Periodic Table.
• Identify them as transition metals, which occupy the d-block and have incomplete d subshells.
• Recall key properties of transition metals: metallic nature, variable oxidation states, and formation of colored compounds.
• Confirm all three elements exhibit these properties due to d-orbital involvement.

Why A is correct:

• Transition metals, per the Periodic Table definition, display metallic conductivity, multiple oxidation states (from d-electron promotion), and colored ions (from d-d electron transitions).

Why the others are wrong:

• B excludes property 3, but all form colored compounds via d-electron transitions.
• C excludes property 2, but all show variable oxidation states like +2 and +3.
• D excludes property 1, but all are solid metals with high melting points and conductivity.

Final answer: A