# How do the number of valence electrons differ across a period?

Jun 15, 2017

The number of valence electrons increases sequentially.......

#### Explanation:

The number of valence electrons increases sequentially.......across the Periodic Table, from left to right as we face the Table.

And take the first Period; hydrogen has ONE valence electron; and helium has TWO valence electrons. And clearly the number of valence electrons influences the reactivity of the element.

And start a new Period, lithium ($\text{Group 1}$) has ONE valence electron; beryllium ($\text{Group 2}$) has TWO valence electrons; boron ($\text{Group 13}$) has THREE valence electrons; carbon ($\text{Group 14}$) has FOUR valence electrons......................