The ionic radii of O2–, F–, Na+ and Mg2+ are in the order :

The first ionization energy (in kJ/mol) of Na, Mg, Al and Si respectively, are :

The five successive ionization enthalpies of an element are 800, 2427, 3658, 25024 and 32824 kJ mol–1. The number of valence electrons in the element is :

Among the statements (I – IV), the correct ones are: (I) Be has smaller atomic radius compared to Mg. (II) Be has higher ionization enthalpy than Al. (III) Charge/radius ratio of Be is greater than that of Al. (IV) Both Be and Al form mainly covalent compounds.

The atomic number of the element unnilennium is :

Three elements X, Y and Z are in the 3rd period of the periodic table. The oxides of X, Y and Z, respectively, are basic, amphoteric and acidic. The correct order of the atomic numbers of X, Y and Z is :

In general the property (magnitudes only) that show an opposite trend in comparison to other properties across a period is

The electronic configurations of bivalent europium and trivalent cerium are (atomic number : Xe = 54, Ce = 58, Eu = 63)

The first and second ionisation enthalpies of a metal are 496 and 4560 kJ mol–1, respectively. How many moles of HCl and H2SO4, respectively, will be needed to react completely with 1 mole of the metal hydroxide ?

The electron gain enthalpy (in KJ/mol) of fluorine, chlorine, bromine and iodine, respectively are:

Within each pair of elements F & Cl, S & Se, and Li & Na, respectively, the elements that release more energy upon and electron gain are :

The third ionization enthalpy is minimum for :

The increasing order of the atomic radii of the following elements is :- (a) C (b) O (c) F (d) Cl (e) Br

B has a smaller first ionization enthalpy than Be. Consider the following statements : (I) It is easier to remove 2p electron than 2s electron (II) 2p electron of B is more shielded from the nucleus by the inner core of electrons than the 2s electrons of Be. (III) 2s electron has more penetration power than 2p electron. (IV) atomic radius of B is more than Be (Atomic number B = 5, Be = 4) The correct statements are :

The acidic, basic and amphoteric oxides, respectively, are :

The one that is NOT suitable for the removal of permanent hardness of water is :

Dihydrogen of high purity (> 99.95%) is obtained through :

Hydrogen peroxide, in the pure state, is :

The equation that represents the water-gas shift reaction is :

If the boiling point of H2O is 373 K, the boiling point of H2S will be :