The element that does NOT show catenation is :

Molecules of benzoic acid (C₆H₅COOH) dimerise in benzene. 'w' g of the acid dissolved in 30 g of benzene shows a depression in freezing point equal to 2K. If the percentage association of the acid to form dimmer in the solution is 80, then w is – (Its given that K_f = 5 K kg mol^–1, Molar mass of benzoic acid = 122 g mol^–1)

The correct order of atomic radii is :

If the de Broglie wavelength of the electron in n^th Bohr orbit in a hydrogenic atom is equal to 1.5 $$\pi $$a₀ (a₀ is Bohr radius), then the value of n/z is -