nonanions
Nonanions are a class of hypothetical chemical species that carry a net negative charge of nine. The term is derived from the prefix "non-" meaning nine and "-anion" referring to a negatively charged ion. In standard chemical nomenclature, ions are typically named based on their charge, with univalent anions (charge -1) often ending in "-ide," bivalent anions (charge -2) also sometimes using "-ide" or other specific nomenclature, and higher charged anions being less common and often having specific names.
The existence of a stable nonanion in isolation or in common chemical compounds is considered highly improbable.