How can chlorine have 10 electrons around it in chlorine trifluoride?
Interhalogens consist of one $\ce{X-F}$ pair whith a regular two electron bond, and pairs of flourine atoms taking over one free electron pair of X (chlorine, bromine, iodine).

What forms are three-centre four-electron bonds (one pair of electrons from the chlorine, two single electrons from two fluorine atoms). That's why interhalogens always have an uneven number of fluorine atoms (except for the dimer $\ce{Cl_2F_6}$).

https://en.wikipedia.org/wiki/Three-center_four-electron_bond

If this is still octet rule is debatable, or at least not directly obvious (see the wp article). Let's just say that fluorine is a bad, bad guy who has things his way.