Here's why:
* Alkali Metals (Group 1): These elements have one electron in their outermost (valence) shell. They are highly reactive and tend to lose this electron to form positively charged ions with a +1 charge. Examples include lithium (Li), sodium (Na), and potassium (K).
* Alkaline Earth Metals (Group 2): These elements have two electrons in their valence shell. They are also reactive but less so than alkali metals. They tend to lose these two electrons to form positively charged ions with a +2 charge. Examples include beryllium (Be), magnesium (Mg), and calcium (Ca).
Important Note: While the number of valence electrons defines these groups, there are other factors that influence their chemical behavior.
