When the nucleus of a uranium atom is bombarded with neutrons and splits into two nuclei of nearly equal mass, this nuclear process is called what?

Introduction / Context:
Nuclear reactions involve changes in the nucleus of an atom and can release enormous amounts of energy. Two major types of nuclear reactions are nuclear fission and nuclear fusion. Understanding the difference between them is important in both physics and general science because they are the basis of nuclear power plants and nuclear weapons. This question describes a situation where a uranium nucleus is bombarded with neutrons and breaks into two smaller nuclei of approximately equal mass, and asks you to name this process.

Given Data / Assumptions:

• The element involved is uranium, a heavy nucleus commonly used as nuclear fuel.
• The uranium nucleus is bombarded with neutrons.
• After bombardment, the nucleus splits into two smaller nuclei of nearly equal mass.
• Energy and additional neutrons are typically released in the process.
• The options include nuclear fission, nuclear fusion, physical change and types of radioactivity.

Concept / Approach:
Nuclear fission is the splitting of a heavy nucleus into two or more lighter nuclei, accompanied by the release of energy and often additional neutrons. This process is induced in reactors by bombarding fissile nuclei such as uranium 235 with slow neutrons. Nuclear fusion, in contrast, involves the joining of two light nuclei to form a heavier nucleus, as occurs in the sun. Physical change refers to changes in state or form without altering the identity of the substance and does not involve nuclear transformations. Artificial and natural radioactivity describe spontaneous nuclear decays, not induced splitting by neutron bombardment. Therefore, the described process is nuclear fission.

Step-by-Step Solution:
Step 1: Identify that uranium is a very heavy element with a large nucleus, which is a typical candidate for fission reactions. Step 2: Note that the process begins when neutrons are fired at the uranium nucleus, indicating an induced nuclear reaction. Step 3: The nucleus then splits into two smaller nuclei of nearly equal mass, which is characteristic of fission, not fusion. Step 4: Nuclear fusion would involve two light nuclei such as isotopes of hydrogen combining to form a heavier nucleus, which is not described here. Step 5: Physical change would not involve any change in the nucleus; it applies to changes in phase, shape or size only. Step 6: Artificial or natural radioactivity describe different patterns of nuclear decay, usually involving emission of alpha, beta or gamma radiation rather than splitting into two large fragments due to neutron bombardment. Step 7: Therefore, the described splitting of uranium nuclei after neutron bombardment is nuclear fission.

Verification / Alternative check:
Descriptions of nuclear reactors and atomic bombs always refer to uranium 235 undergoing fission when it absorbs a neutron. A typical reaction is a uranium 235 nucleus absorbing a neutron and splitting into two medium sized nuclei such as barium and krypton, plus additional neutrons and a large amount of energy. This chain reaction, where released neutrons cause further fission events, is the basis of nuclear power generation. Textbooks use phrases like uranium nucleus splits into two smaller nuclei to define nuclear fission. This matches the description in the question exactly and confirms fission as the correct term.

Why Other Options Are Wrong:
Option B, nuclear fusion, describes the process where two light nuclei, such as deuterium and tritium, collide and fuse to form a heavier nucleus, releasing energy. This is not what happens when a uranium nucleus is split. Option C, physical change, refers to non nuclear changes in state or appearance and does not involve any change in the nucleus. Option D, artificial radioactivity, involves inducing radioactivity by bombardment but usually refers to the production of new radioactive isotopes, not the large scale splitting of a heavy nucleus. Option E, natural radioactivity, is spontaneous and not triggered by neutron bombardment. Only option A accurately describes the process in the question.

Common Pitfalls:
Students sometimes confuse fusion and fission because both release energy and the words sound similar. A useful memory aid is that fission begins with a heavy nucleus that splits into lighter parts, while fusion begins with light nuclei that fuse into something heavier. Another pitfall is to treat any nuclear change as radioactivity without distinguishing between induced chain reactions and spontaneous decay. Keeping a clear mental image of uranium fuel rods in reactors undergoing fission, and hydrogen nuclei in stars undergoing fusion, helps avoid such confusion in exam questions.

Final Answer:
The process where a uranium nucleus splits into two nuclei of nearly equal mass after neutron bombardment is called Nuclear fission.