Why Do The Alkali Metals Form 1+ Ion When The Alkali Earth Metals Form 2+ions?
Alkali metals are in group I of the periodic table and include the elements, sodium, potassium and lithium. These elements have their electrons arranged around the nucleus in shells and they have one electron in their out shell. When the alkali metals form ions, they do so by losing this electron and therefore becoming positively charged. Because they lose one electron, they have a charge of one +. So, Lithium forms ions with the formula Li+ and have a valency of one. This means that if they react with a negatively charged ion that needs two electrons to complete its outer shell, two atoms of litium are needed to form the compound. The alkali earth metals are in group 2 of the periodic table and they include the metals calcium and magnesium. These elements have two electrons in their outermost electron shell and when they form ions, they lose these electrons, becoming positively charged. Their ions have the formula Ca2+ and Mg 2+ because two electrons have been lost.
