Final answer:
Group 2A elements form cations with a 2+ charge by losing two electrons. These cations are isoelectronic with the nearest noble gas. Some heavier elements and transition metals can form ions with multiple charges, which are less predictable.
Step-by-step explanation:
Formation of Group 2A Ion Cations
When elements from Group 2A of the periodic table form ions, they typically lose two electrons. This loss occurs because Group 2A elements, also known as the alkali earth metals, have two s orbital electrons in their outer shell. Upon ionization, they become cations with a 2+ charge. For instance, a calcium (Ca) atom loses two electrons, resulting in a Ca2+ ion. These cations are isoelectronic with the nearest noble gas, having the same electron configuration after losing their valence electrons. This predictable behavior is useful when examining the periodic table to determine the charge of ions formed by main-group elements.
However, there are exceptions to this rule, especially with heavier elements where the inert pair effect comes into play, leading to varying oxidation states. For example, tin (Sn) may form Sn2+ or Sn4+ ions. Furthermore, transition metals such as iron can form multiple cationic charges (Fe2+ or Fe3+), which are less predictable based on their position in the periodic table.