Successive (IE) values of three elements of third period are given below

Elements	(IE1)	(IE2) (in KJmol–1)	(IE3)
X	513	4562	6920
Y	738	1451	7733
Z	1521	2666	3931

Atomic numbers of X, Y and Z respectively are

In the element "X" sudden jump in IP₂  is observed . Thus element "X" is a first group element
IP₃ of element "Y" is abnormally high. Thus "Y" is a second group element
X,Y,Z belong to third period.
IP  of Z is very high compared to that of X and Y. Moreover no abnormal jump in its IP₂ and IP₃ values.
Z must be a noble gas.
from inspection the atomic number of X,Y,Z are 11,12,18.