* Increasing Nuclear Charge: As you move across a period, the number of protons in the nucleus increases. This stronger positive charge attracts the electrons more strongly.
* Similar Electron Shielding: While the number of electrons increases across a period, they all occupy the same energy level. This means the shielding effect of inner electrons remains relatively constant.
* Effective Nuclear Charge: The increased nuclear charge and constant shielding lead to a higher effective nuclear charge. This means the outermost electrons experience a stronger attraction to the nucleus, pulling them closer and resulting in a smaller atomic radius.
In summary: Across a period, the stronger attraction between the nucleus and the outermost electrons due to increasing nuclear charge and constant shielding leads to a decrease in atomic radius.
