TRENDS IN ATOMIC RADIUS

 TRENDS IN ATOMIC RADIUS:

•Definition: "The distance of outermost electrons from the nucleus of an atom while considering it spherical is called atomic radius"

Trend:

Along the period:

•The size of atoms and ions decreases from left to right along with period. In a given period, the number of shells in all the elements remains the same. 

Reason:

Reason is that the value of effective nuclear nuclear charge increases from left to right due to increase in number of protons. The increased effective nuclear charge pulls the electron cloud of atom closer to the nucleus. Thus, the size of the atoms and ions goes on decreasing from left to right.

•In any period, the alkali metals are present at the extreme left of the periodic table. Hence, they have largest size in any period.

•In any period, the halogens are present at the extreme right of the periodic table (excluding noble gases). Hence, they have smallest size in any period.

Along the group:

Atomic radius increase when we move from top to bottom.

Reason :Reason is that when we move from top to bottom no of shell increases.

Example: Sodium is larger in size then lithium because lithium has 2 shells while sodium has three shells.

 Structure of lithium

                       Structure of sodium