The octet rule is a general guideline that suggests atoms tend to gain, lose, or share electrons in order to achieve a stable electron configuration with 8 valence electrons. However, there are exceptions to the octet rule, particularly for elements in the third period (and beyond) of the periodic table.
To determine the maximum number of valence electrons for an atom that does not follow the octet rule, you need to consider its position in the periodic table and its electron configuration.
Identify the group (column) of the element: The group number of an element in the periodic table indicates the number of valence electrons it can potentially have. For example, elements in Group 1 have 1 valence electron, elements in Group 2 have 2 valence electrons, and so on.
Consider the atom's electron configuration: The electron configuration of an atom shows how the electrons are distributed among different energy levels and orbitals. By examining the electron configuration, you can determine the number of valence electrons.
For elements in the third period (and beyond), such as phosphorus (P) or sulfur (S), the maximum number of valence electrons can exceed 8 due to the availability of additional d orbitals. These elements can have expanded octets and accommodate more than 8 electrons in their valence shells.
To summarize, to determine the maximum number of valence electrons for an atom that does not follow the octet rule, you should identify the element's group number and consider its electron configuration, taking into account the possibility of expanded octets for elements in the third period and beyond.