How can elements achieve a stable electron configurations?
A stable electron configuration for the representative or main group elements is a noble gas configuration. The main group or representative elements are in Groups 1, 2, 13-18 (IA, IIA, IIIA - VIIIA) on the periodic table. The noble gases are in Group 18 (VIIIA). Atoms of the representative elements achieve a noble gas configuration by gaining or losing electrons and becoming ions, or by sharing electrons.
Helium (He), in Period 1, is the first noble gas and has an electron configuration of
In Period 2, lithium atoms (
The rest of the representative elements (Groups 1, 2, 13-17), will follow the same pattern as the Period 3 elements. The atoms of the Group 1 and 2 elements will lose their valence electrons in order to achieve the electron configuration of the noble gas in the previous period, and the atoms of the Groups 13-17 elements will lose, gain, or share electrons in order to achieve the electron configuration of the noble gas at the end of that period.
The transition elements (Groups 3-13) behave differently, and many form ions of more than one charge, such as iron (Fe), which can form 2+ and 3+ ions. But they still lose electrons to form positively charged ions with stable electron configurations, but not noble gas configurations.