Atomic Radii Trends in Periodic Table.

Received Questions: What is Atomic Radii Trends in Periodic Table? How atomic radii vary within a group? What is the trend of atomic radii across period in Modern Periodic table? Why atomic radius decrease from left to right? Why atomic radii increase from top to bottom is a group?

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Atomic Radii Trends in Periodic Table:

Under this heading, you will find the Atomic Radii trends in Periodic Table within Group and across the period.

Variation across a Period:

The atomic radii decreases from left to right in a period.


The decreasing trend in a period is due to the increase in the nuclear charge. As the nuclear charge increases, the pull on the electrons is increased and size of an atom decreases. Moreover, the shielding effect remains the same from left to right in a period.

Variation across a Group:

The atomic radii increases from top to bottom in a group of the Periodic Table.


The increase in atomic radii is due to increase in the number of shells and the screening effect. The screening effect is also called shielding effect. This is responsible for the decrease in force of attraction of the nucleus for the electrons present in the valance shell.

Periodic Pictures:

Learning Outcomes:

  • Atomic radii trends in periodic table.
  • atomic radii across period.
  • atomic radii within group.
  • Reason for decreasing and increasing atomic radii in period and group.



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Fawad's Chemistry

Hope you fine. I'm Fawad and author of this blog "Chemanalogy". Love to write on Chemistry. Currently teaching A Levels, O Levels and University Chemistry offline as well as online. Connect to chemanalogy community by subscribing via email.