* Increased Nuclear Charge: As you move across a period, the number of protons in the nucleus increases. This leads to a stronger positive charge attracting the electrons.
* Same Electron Shell: Electrons are added to the same energy level (same electron shell) as you move across a period.
* Shielding Effect: While the number of electrons increases, the number of inner electron shells remains the same. This means the shielding effect from the inner electrons on the outermost electrons remains relatively constant.
Combined Effect: The increased nuclear charge pulls the electrons closer to the nucleus, outweighing the effect of the increased electron-electron repulsion. This results in a smaller atomic radius.
Example:
* Lithium (Li) has a larger atomic radius than Fluorine (F) because Li has a smaller nuclear charge and its outermost electron is further from the nucleus.
