Assertion: Chromium dissolves in nickel to form Cr - Ni alloy.

Reason: An alloy is formed due to the similar sizes of the atoms of transition elements.

Assertion and Reason both are correct statements and reason is the correct explanation for assertion.

Transition metals mix freely with each other in the molten state and on cooling a solution of different metals result in the formation of alloy.

Example: Chromium dissolves in nickel to form Cr - Ni alloy.

The alloy formation is explained on the basis of similar sizes of the atoms of these metals which allow the atoms one metal to take up the positions in the crystal lattice of the other.