Property used by Mendeleev to classify the elements was -

1. Brightness

2. Atomic weight or mass

3. Number of isotopes

4. Lustre

The basic difference between Mendeleev’s Periodic Law (A) and Modern Periodic Law (B) is:

The period and group number of the element with Z =114 are:

The atomic number of the element present in the 3rd period and 17th group of the periodic table would be -

1. 18

2. 23

3. 24

4. 17

The similarity in physical and chemical properties in a group of periodic table is due to the -

1. Same atomic number

2. Same number of valence electrons.

3. Same atomic mass

4. Same number of isotopes

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 :

Anions are larger in radius than their parent atoms because:

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 explanation for the fact that the first ionization enthalpy of sodium is lower than that of magnesium but its second ionization enthalpy is higher than that of magnesium would be -

1) pressure and volume

2) lustre and brightness

3) atomic size and effective nuclear charge

4) availability in nature