Number of molecules from the following which are exceptions to octet rule is ____.
\(\text{CO}_2, \, \text{NO}_2, \, \text{H}_2\text{SO}_4, \, \text{BF}_3, \, \text{CH}_4, \, \text{SiF}_4, \, \text{ClO}_2, \, \text{PCl}_5, \, \text{BeF}_2, \, \text{C}_2\text{H}_6, \, \text{CHCl}_3, \, \text{CBr}_4\)