The atomic numbers of the three elements X, Y and Z are 2, 6 and 10 respectively. (i) Which … to the same period? Give reasons for…
(i) X and Z.
X and Z have zero valency hence they belong to same group: noble gases.
(ii) Y and Z.
Y: 2,4 and Z: 2,8 so, both of them belong to second period with two shells filled.