Which of the following statement is wrong?

Down the group always for transition elements the atomic radii increase.

The correct answer is option (4) Down the group always for transition elements the atomic radii increase.

The atomic radii of the transition elements do not always increase down the group. The atomic radii of the third transition elements are smaller than the corresponding second transition elements. This is because of the lanthanide contraction.

The lanthanide contraction is a phenomenon in which the atomic radii of the lanthanide elements decrease as you go down the group. This is due to the increase in nuclear charge of the lanthanide elements. The increased nuclear charge pulls the electrons closer to the nucleus, making the atoms smaller.

The lanthanide contraction affects the atomic radii of the third transition elements because the third transition elements have the same electron configuration as the lanthanide elements. This means that the third transition elements have the same number of electrons as the lanthanide elements, but they have a smaller nuclear charge. As a result, the third transition elements are smaller than the second transition elements.

The other statements are correct.

•Statement (1) is correct. The melting points and boiling points of the transition elements increase as you go down the periodic table. This is because the transition elements become larger as you go down the periodic table, and the larger atoms have stronger metallic bonds.

•Statement (2) is correct. The ionization energies of the third transition elements are greater than the corresponding second transition elements. This is because the third transition elements have a larger nuclear charge than the second transition elements. The larger nuclear charge pulls the electrons closer to the nucleus, making it more difficult to remove them.

•Statement (3) is correct. The atomic radii of the third transition element after Hf are almost the same as that of the second transition element right above it. This is because the lanthanide contraction causes the atomic radii of the third transition elements to be smaller than expected.

Therefore, the only statement that is incorrect is statement (4). The atomic radii of the transition elements do not always increase down the group. The atomic radii of the third transition elements are smaller than the corresponding second transition elements.