Question

a neutron strikes an atom of uranium - 235 to start a fission reaction. a student expresses this situation as $_{1}^{0}\text{n}+_{92}^{235}\text{u}$. which statement describes why the expression is incorrect? (1 point)
a neutron should be expressed as $_{0}^{1}\text{n}$, not $_{1}^{0}\text{n}$.
the atomic number for uranium - 235 is in the wrong location.
the mass number for uranium - 235 is in the wrong location.
a neutron should be expressed as $_{1}^{1}\text{h}$, not $_{1}^{0}\text{n}$.

Explanation:

• For a neutron, the mass number is \(1\) (since it has a mass approximately equal to a proton) and the atomic number is \(0\) (as it has no charge). So the correct symbol is \(_{0}^{1}\text{n}\).
• The symbol for an element is written as \(_{Z}^{A}\text{X}\), where \(Z\) is the atomic number and \(A\) is the mass number. For uranium - 235 (\(\text{U}\)), \(Z = 92\) (atomic number) and \(A=235\) (mass number), and the given \(_{92}^{235}\text{U}\) has the atomic number and mass number in the correct positions.
• \(_{1}^{1}\text{H}\) is the symbol for a proton (hydrogen - 1 nucleus), not a neutron.

Answer:

A. A neutron should be expressed as \(_{0}^{1}\text{n}\), not \(_{1}^{0}\text{n}\).