The main group elements tend to lose or gain the number of electrons needed to get the same number of electrons as the nearest noble gas.
![valence electron trend periodic table valence electron trend periodic table](https://wisc.pb.unizin.org/app/uploads/sites/126/2017/08/CNX_Chem_06_05_CovalradiT.jpg)
Z eff increases across a period ⇒ the atomic radius decreases across a period
![valence electron trend periodic table valence electron trend periodic table](https://useruploads.socratic.org/lwBgHfP3Tcm4X0KFc993_800px-periodic_table_structure.svg.png)
The higher the effective nuclear charge Z eff, the more attracted the outer electrons are to the nucleus and the closer they are to the it.
![valence electron trend periodic table valence electron trend periodic table](https://i.pinimg.com/736x/2f/c6/5a/2fc65aca862ec9d15de9f479784d46c9.jpg)
The distance between the nucleus and the outermost electrons Elements of the same period have similar valence electron configurations and therefore behave in the same way during a chemical reaction The properties of elements depend on their valence electrons.