At 143K, the reaction of  $Xe{F}_4$ with $O_2{F}_2,$ produces a xenon compound  $Y.$ The total number of lone pair(s) of electron present on the whole molecule of $Y$  is _________

$Xe{F}_4+O_2{F}_2\underset{ }{\overset{ }{\to }}Xe{F}_6+O_2$

Shape of  $Xe{F}_6$ is distorted octahedral contains one lone pair  $e^{-}s$ on central atom 3 lone pair  $e^{-}s$ each F atom surrounded by $Xe.$ 
Total no.of lone pairs  $:1+18=19$