A neutron strikes an atom of uranium-235 to start a fission reaction. A student expresses this situation as 0/1n + 235/92 U. Which statement describes why the expression is incorrect?
A. The mass number for uranium-235 is in the wrong location.
B. A neutron should be expressed as 1/0n, not 0/1n.
C. A neutron should be expressed as 1/1n, not 0/1n.
D. The atomic number for uranium-235 is in the wrong location.
B. A neutron should be expressed as 1/0n, not 0/1n.
The correct answer is C. A neutron should be expressed as 1/1n, not 0/1n.
In nuclear notation, the top number represents the mass number (number of protons and neutrons) and the bottom number represents the atomic number (number of protons). The correct notation for a neutron is 1/1n, indicating it has a mass number of 1 and an atomic number of 0.
To determine the correct statement, let's break down the given expression: 0/1n + 235/92 U.
- The first part, 0/1n, represents a neutron. Neutrons are typically written as 1/0n, not 0/1n. This is because the denominator (the bottom number) represents the atomic number, which is always positive and non-zero. Therefore, option B states the correct reason why the expression is incorrect.
Option A is incorrect because the mass number for uranium-235 is correctly placed in the expression.
Option C is incorrect because although a neutron can also be expressed as 1/1n, it can still be expressed as 1/0n, which is more commonly used.
Option D is incorrect because the atomic number for uranium-235 is correctly placed in the expression.