CBSE Class 10 Science 2020 · Paper 31/3/2 · Question 17

(a) X > Y > Z (nitrogen > oxygen > fluorine). The three are in the same period, and the nuclear charge increases from X to Z while the electrons stay in the same two shells, so the atoms get smaller. (b) Z (fluorine, 2, 7) is the most electronegative. It needs only one electron to attain the stable configuration 2, 8, and as the smallest atom with the largest nuclear charge it attracts electrons most strongly. (c) (i) ${\text{X}}_2{\text{Y}}_3$ (that is, ${\text{N}}_2{\text{O}}_3$); (ii) ${\text{XZ}}_3$ (that is, ${\text{NF}}_3$).