Exponential numbers in table?

Is there a way to create a table containing numbers in scientific notation (with exponents)? I would like to have one column in a table handle numbers from 1E-9 to 1E+9, without defining it like this

	create table t1
		( x  number(19,9) );

If I do create a table with many numbers like this, what are the trade-offs in performance or space?

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Glenn Schuette                   
schuette_at_ti.com