The graph given below illustrates the correlation between the number of protons (x-axis) and the number of neutrons (y-axis) for elements A, B, C, D, and E in the periodic table. These elements are denoted by the letters rather than their conventional symbols.
(a) Identify the radioactive radiation emitted when element C decays into element E. Represent this using a nuclear reaction.
(b) What is the special name given to elements like D and E?
(c) If element C transforms into element B by emitting a radioactive ray, how will this ray behave in an electric field?
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(a) From the graph,
Number of protons in C = 92
Number of neutrons in C = 146
Mass number of C = Number of protons in C + Number of neutrons in C = 92 + 146 = 238
Number of protons in E = 93
Number of neutrons in E = 145
Mass number of E = Number of protons in E + Number of neutrons in E = 93 + 145 = 238
Since element C has one less proton and one neutron more than the element E, if C decays into E, its proton number increases by one and its neutron number decreases by one, keeping the mass number the same, which happens only in the case of beta radiation.
Thus, the reaction will be as follows :
23892C → 23893E + 0-1β
(b) As points D and E are situated on the same vertical line but on different horizontal lines, they have the same number of protons but different numbers of neutrons, i.e., their atomic number is the same but their mass numbers are different, so they are isotopes of each other.
(c) Number of protons in B = 90
Number of neutrons in B = 144
Mass number of B = Number of protons in B + Number of neutrons in B = 90 + 144 = 234
As element B has two protons less than element C and a mass number four less than that of C, during the decay of C into B, two protons and two neutrons are emitted, which is nothing but an alpha particle.
Alpha particles shift towards the negative plate in an electric field.