Number of lone pairs on bonded atoms is equal to ‘X’ .Number of lone pairs/central atom is equal to ‘Y’ . X-Y is equal to ten in
BrF5
SF6
XeF4
XeF2
Number of electron pairs(EP)=V+M-C+A2; V=Group number of central atom; M=-H, -X, -OH....monovalent groups attached to central atom ; C=Charge of cation ; A=Charge of anion ; V=6,7,8 respectively for 16th, 17th, 18th group elements ; Number bond pairs, BP(according to VSEPR theory)=Number of atoms directly attached to central atom; =6,5,4, respectively in SF6, BrF5, XeF4 ; Number lone pairs on central atom(LP)=EP-BP ; =0,1,2 respectively in SF6, BrF5, XeF4 ; SF6-'6' bp +'0' lp on central atom; sp3d2-Squre bipyramidal (or) Octahedral ; 18 lone pairs/molecule BrF5-'5' bp +'1' lp on central atom ; sp3d2-Squre pyramidal ; 16 lone pairs/molecule XeF4-'4' bp +'2' lp on central atom ; sp3d2-Square planar ; 14 lone pairs/molecule Note; Each bonded halogen atom has '3' lone pairs on it ; Orientation of electron pairs is octahedral (or) Square bipyramidal in all the three molecules ;