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Ch.2 - Atoms & Elements
Chapter 2, Problem 56

Determine the number of protons and neutrons in uranium-235, which is used in nuclear fission, and write its symbol in the form AZX.

Verified step by step guidance
1
Identify the atomic number (Z) of uranium, which is 92. This number represents the number of protons in the nucleus.
Recognize that the mass number (A) of uranium-235 is 235. This number is the sum of protons and neutrons in the nucleus.
Calculate the number of neutrons by subtracting the atomic number (Z) from the mass number (A): Neutrons = A - Z.
Write the symbol for uranium-235 in the form A^ZX, where A is the mass number, Z is the atomic number, and X is the chemical symbol for uranium (U).
Combine the information to express uranium-235 as 235^92U, indicating its composition of protons and neutrons.

Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Atomic Structure

Atoms consist of protons, neutrons, and electrons. Protons are positively charged particles found in the nucleus, while neutrons are neutral particles that also reside in the nucleus. The number of protons defines the element, while the total number of protons and neutrons gives the atomic mass.
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Atom Structure

Isotopes

Isotopes are variants of a chemical element that have the same number of protons but different numbers of neutrons. For example, uranium-235 has 92 protons (as all uranium isotopes do) and 143 neutrons, distinguishing it from other isotopes like uranium-238, which has 146 neutrons.
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Nuclear Fission

Nuclear fission is a process in which the nucleus of an atom splits into smaller parts, releasing a significant amount of energy. Uranium-235 is a key fuel in nuclear reactors because it can sustain a chain reaction when it absorbs a neutron, leading to the release of energy and more neutrons.
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