Let's assume that the number of protons in X is equal to ′a′ Thus, number of neutrons becomes 0.166a+a=1.166a since, Mass number = Number of protons + Number of neutron 52=a+1.166a 52=2.166a a=24 '24' protons signify that the element X is 24Cr Now, let's assume that the number of protons in Y is equal to ′b′. Thus, number of neutrons becomes 0.273b+b=1.273b since, Mass number = Number of protons + Number of neutron 75=b+1.273b 75=2.273b b=33 ‘33’ protons signify that the element Y is 33As .