The de Broglie wavelength ($$\lambda$$) associated with a photoelectron varies with the frequency (v) of the incident radiation as, [v0 is threshold frequency] :

What is the work function of the metal if the light of wavelength 4000$$\stackrel{\circ }{A}$$ generates photoelectrons of velocity 6 $$\times$$ 105 ms–1 from it ? (Mass of electron = 9 $$\times$$ 10–31 kg; Velocity of light = 3 $$\times$$ 108 ms$$-$$1 Plank's constant = 6.626 $$\times$$ 10–34 Js; Charge of electron = 1.6 $$\times$$10–19 JeV–1)

The ground state energy of hydrogen atom is – 13.6 eV. The energy of second excited state of He+ ion in eV is :

In general, the properties that decrease and increase down a group in the periodic table, respectively, are :

In comparison to boron, berylium has :

Among the following, the energy of 2s orbital is lowest in :

The element having greatest difference between its first and second ionization energies, is :

The IUPAC symbol for the element with atomic number 119 would be :

The lathanide ion that would show colour is :

The size of the iso-electronic species Cl–, Ar and Ca2+ is affected by :

The element with Z = 120 (not yet discovered) will be an/a -

The correct option with respect to the Pauling electronegativity values of the element is :

The correct order of the atomic radii of C, Cs, Al, and S is :

The electronegativity of aluminium is similar to :

When the first electron gain enthalpy $$\left({\Delta }_{eg}H\right)$$ of oxygen is $$-$$ 141 kJ/mol, its second electron gain enthalpy is :

Aluminium is usually found in +3 oxidation state. In contrast, thallium exists in + 1 and + 3 oxidation states. This is due to :

The metal that gives hydrogen gas upon treatment with both acid as well as base is :

The temporary hardness of a water sample is due to compound X. Boiling this sample converts X to compound Y. X and Y, respectively, are :

The correct statements among (a) to (d) are : (a) saline hydrides produce H2 gas when reacted with H2O. (b) reaction of LiAlH4 with BF3 leads to B2H6. (c) PH3 and CH4 are electron - rich and electron - precise hydrides, respectively. (d) HF and CH4 are called as molecular

The synonym for water gas when used in the production of methanol is :