<Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2011) (Learn how and when to remove this template message) </Td> </Tr> </Table> <Tr> <Td> </Td> <Td> This article needs additional citations for verification . Please help improve this article by adding citations to reliable sources . Unsourced material may be challenged and removed . (March 2011) (Learn how and when to remove this template message) </Td> </Tr> <P> The Thorpe's Crisscross method is a method of finding out the chemical formula of a metal and non-metal that combine to form an ionic bond created by high school chemistry teacher Kim Thorpe . </P> <P> To use this method, the absolute value of the oxidation number of the first ion is used as the subscript of the second, and vice versa . The subscripts are then reduced by the greatest common factor . For instance, to find the formula for aluminium oxide: </P>

When do you use the criss cross method in chemistry
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