To understand the question, please, see the attached figure which represents the transmutation equation properly.
Also, you can take into account the set of answer choices that comes with this question:
A) uranium-242
B) uranium-243
C) curium-245
D) uranium-245
E) curium-242
Answer: option E) curium-242Explanation:
You have to see the attached figure for the right representation of the transmutation equation.
In that you see:
i) Plutonium-239 isotope, showing 239 mass number (superscript to the left of the symbol of the element) and 94 atomic number (subscript to the left of the symbol of the element)
ii) Helium-4 atom, showing 4 mass number (superscript to the left of the symbol) and 2 atomic number (subscript to the left of the symbol)
iii) empty space for the element that you have to determine
iv) a neutron, whose superscript to the left is 1 meaning 1 mass number, and its subscript to the left is 0 meaning 0 protons.
Then,
this balance tells you the mass number and atomic number of the element missing:Mass number: 239 + 4 = x + 1 ⇒ x = 239 + 4 - 1 = 242Atomic number: 94 + 2 = x + 0 ⇒ x = 96.
Remember that
the atomic number identifies the element and the mass number identifies the isotope.Then, given that the resultant atomic number of the missing element is 96, you find in the periodic talble that
the element is Curium (Cm). And given the mass number is 242,
the isotope is Curium - 242.And that is the answer: Curium - 242
