A neutron strikes an atom of uranium-235 to start a fission reaction. A student expresses this situation as 0/1n + 235/92U.Which statement describes why the expression is incorrect?
The mass number for uranium-235 is in the wrong location
The atomic number for uranium-235 is in the wrong location
The atomic number for uranium-235 is in the wrong location.
The correct answer is: The atomic number for uranium-235 is in the wrong location.
In the expression 0/1n + 235/92U, the atomic number (92) for uranium-235 is placed at the denominator, which is incorrect. The atomic number usually appears at the top left as a subscript to the symbol of the element, while the mass number appears at the top left as a superscript. Therefore, the correct notation for uranium-235 should be ^(235)U, where the 235 is the mass number and the U is the symbol for uranium.
The correct statement is: The atomic number for uranium-235 is in the wrong location.
In order to properly represent an atom or isotope, the atomic number (which represents the number of protons in the nucleus) is typically written as a subscript and the mass number (which represents the total number of protons and neutrons in the nucleus) is written as a superscript.
For example, the correct notation for Uranium-235 would be ^(235)U or U-235, where 235 is the mass number and U is the symbol for uranium.