Question

The general trends observed for how atomic radii change within a group can be explained by ___(i)___. The general trends for how atomic radii change within a period can be explained by ___(ii)___.

(i) principal quantum number of the valence electrons; (ii) population of different subshells within an energy level

(i) population of different subshells within an energy level; (ii) principal quantum number of the valence electrons

(i) principal quantum number of the valence electrons; (ii) effective nuclear charge felt by the valence electrons

(i) effective nuclear charge felt by the valence electrons; (ii) principal quantum number of the valence electrons

(i) population of different subshells within an energy level; (ii) effective nuclear charge felt by the valence electrons

Answer 1

1) General trends observed for how atomic radii change within a group can be explained by -

principal quantum number of the valence electrons

As we go down the group new shells are added which increases the principal quantum number and thus due to large size of next higher shell the atomic radii also increases.

2) The general trends for how atomic radii change within a period can be explained by

effective nuclear charge felt by the valence electrons

As we go from left to right in a periodic table the effective nuclear charge felt by electrons increases due to addition of protons and the same position of added electrons and thus they get attracted by a more stronger electrostatic force thus reducing the atomic radii.

Option 1 gives the right answer.