Question

How does atomic size vary in the periodic table?

Answer 1

Hint: We should know what atomic size means and the factor on which the atomic size depends. The radius of an atom is known as atomic size. The atomic size depends upon the effective nuclear charge of the nucleus. Atomic size also depends upon the shell in which the outermost electrons present or the distance between the nucleus and outermost shell.

Complete answer:
- The distance between the nucleus and the boundary of the outermost shell is known as atomic size.
- In the left to right in the periodic table, the electrons get added in the same shell and left to right the proton number hence the positive change or we can say nuclear change increases.
- As the positive charge increases from left to right, the attraction of the nucleus on the electrons of the outermost shell increases. So, left to right in the periodic table size of the atom decreases.
- From top to bottom in the periodic table, the electrons get added in the next higher shell and left to right the proton number hence the positive change or we can say nuclear change increases.
- As the positive charge increases from left to right, the attraction of the nucleus on the electrons of the outermost shell increases but as the electrons are get added in the next higher shell so, the distance between the nucleus and outermost shell increases so, the attraction of the nucleus on outermost shell decreases. So, top to bottom in the periodic table size of the atom increases.

Therefore, in the periodic table, left to right the size of the atom decreases, and top to bottom the size of the atom increases.

Note: On the top left of the periodic table alkali metals are present whose size is maximum in a period. On the top right of the periodic table noble gases are present whose size is minimum in a period. In a group, the atom present at the top has the smallest size and the atom present at the bottom has the largest size. In the periodic table, some exceptions of general trends are also present. Such as the size of oxygen is slightly larger than nitrogen.