Zr and Hf have almost identical atomic radii. Give reason.

(a)Zr and Hf have almost identical radii : Give reason. (b)Name the gas liberated when Lanthanoids (Ln) react wtih acids.

Give reasons: Zr and Hf have almost identical radii.

Give reasons: (i) Zirconium (Z = 40) and Hafnium (Z = 72) have almost similar atomic radii. (ii) d-block elements exhibit more oxidation states than f-block elements. (iii) The enthalpies of atomization of the transition metals are high (iv) The variation in oxidation states of transition metals is of different type from that of the non transition metals. (v) Orange solution of potassium dichromate turns yellow on adding sodium hydroxide to it.

Give reasons : (i) Actinoids show variable oxidation states. (ii) Zr and Hf have almost identical radii.

Out of the elements X and Y, which has bigger atomic radius? Give reason to justify your answer. (i) X has atomic number 18 and atomic mass 40. (ii) Y has atomic number 20 and atomic mass 40.

Give reasons: i) Actinoids show variable oxidation state. ii) Zr and Hfhave almost identical radii.

Transition metals are very hard and have high melting and boiling points. Give reason.

Given below are atomic radii of same elements of second period. {:("Element","B","O","N","C"),("Atomic Radii in pm","88","66","74","77"):} Arrange these elements in the increasing order of their atomic number. Give reason for your answer.

Is copy of DNA formed during reproduction identical to the original cell? Give reason for the support of your answer and explain how DNA copying is beneficial for the species?