Bond length/distance is defined as average distance between niaclei of two bonded atom in a molecules.
Bond length =r1+r2 Element (x)=143pm means it is close to bond length of fluorine (F2). Atomic number =9 Element (Y)=110pm is equal to bond length of nitrogen (N2). Atomic number =7 Element (Z)=121pm is equal to bond length of axygen (O2). Atomic number =8