Which of the following is not an empirical formula?
a) co
b) brcl2
c) c6h9
d) h2o

The correct answer among the choices given is option C. C6H9 is not an empirical formula. Because it can still be reduced to lower proportions. An empirical formula is a formula giving only the proportion of the elements but not the actual number of atoms.

If a hydrogen atom is neutral, it must also have  one electron. an oxygen atom (o) has an atomic number of eight (8). this means a neutral oxygen atom has eight protons and eight electrons. the element actium (ac) has an atomic number of 89, so it has 89 protons and 89 electrons in a neutral atom