To determine the number of neutrons in a uranium ([tex]\( U \)[/tex]) atom with an atomic number ([tex]\( Z \)[/tex]) of 92 and a mass number ([tex]\( A \)[/tex]) of 235, follow these steps:
1. Identify the Atomic Number and Mass Number:
- The atomic number ([tex]\( Z \)[/tex]) of uranium is 92. This number represents the number of protons in the nucleus of the atom.
- The mass number ([tex]\( A \)[/tex]) of the uranium isotope given is 235. This number represents the total number of protons and neutrons in the nucleus.
2. Understand the Relationship:
- The number of neutrons ([tex]\( N \)[/tex]) in the nucleus can be determined by the formula:
[tex]\[
N = A - Z
\][/tex]
where:
- [tex]\( A \)[/tex] is the mass number
- [tex]\( Z \)[/tex] is the atomic number
3. Substitute the Given Values:
- Substitute 235 for [tex]\( A \)[/tex] (mass number) in the formula.
- Substitute 92 for [tex]\( Z \)[/tex] (atomic number) in the formula.
4. Perform the Calculation:
[tex]\[
N = 235 - 92
\][/tex]
5. Result:
[tex]\[
N = 143
\][/tex]
Thus, the number of neutrons in the uranium atom [tex]\({ }_{92}^{235} U\)[/tex] is 143. Therefore, the correct answer is [tex]\( 143 \)[/tex].
