The ionic radius indicates the distance between the nucleus and :

1. outermost shell of an atom.

2. outermost shell of an ion.

3. outermost shell of the cation only.

4. outermost shell of the anion only.

 The trend of atomic radius in a period and a group is :

The energy of an electron in the ground state of the hydrogen atom is $–2.18\times {10}^{-18}J$.  The ionization enthalpy of atomic hydrogen in terms of J ${\mathrm{mol}}^{-1}$ is -

1. 2.81 × 10⁶ J mol${}^{-1}$

2. 1.31 × 10⁶ J mol${}^{-1}$

3. 2.31 × 10⁶ J mol${}^{-1}$

4. 1.81 × 10⁶ J mol${}^{-1}$

The first ionization enthalpy values (in kJ mol^–1) of group 13 elements are :

The explanation for the deviation from the general trend can be -

1. Ga has lower ionization enthalpy than Al.

2. Ga has higher ionization enthalpy than Al.

3. Al has higher ionization enthalpy than Ga. 

4. Ga has a lesser valence electron than Al.

An element with higher negative electron gain enthalpy in the given pair is-

(i) O or F  (ii) F or Cl

The basic difference between the  electron gain enthalpy (E_a) and electronegativity (E_N) is -

The statement that "the electronegativity of N on the Pauling scale is 3.0 in all the nitrogen compounds" is incorrect because -

1. Electronegativity of an element is a variable property.

2. Pauling scale is not used to measure electronegativity.

3. The electronegativity of N on the Pauling scale is 12.0

4. None of the above.

The correct statement about radius is :

The values of first ionization enthalpies for two isotopes would be -

The reactivity of alkali metals increases, whereas halogen decreases down the group, because -