Question

Uranium-235 and uranium- 238 differ in terms of the number of subatomic particles. For which subatomic particle is the number different and by how much?

Short answer

The number of neutrons differs by 3.

Step-by-step solution

Understand the Different Types of Uranium

Uranium-235 and Uranium-238 are isotopes of the element uranium. Isotopes of an element have the same number of protons but different numbers of neutrons.

Identify the Proton Number

Both Uranium-235 and Uranium-238 are forms of uranium, and all uranium atoms have 92 protons. The number of protons, which determines the element, is the same for both isotopes.

Determine the Neutron Number

The difference in mass of the isotopes comes from the different numbers of neutrons. Uranium-235 has 143 neutrons (235 total subatomic particles minus 92 protons), while Uranium-238 has 146 neutrons (238 total subatomic particles minus 92 protons).

Calculate the Neutron Difference

To find out how many more neutrons Uranium-238 has than Uranium-235, subtract the number of neutrons in Uranium-235 from the number in Uranium-238: \(146 - 143 = 3\).

Key concepts

Uranium-235

Uranium-235 is a fascinating isotope of the element uranium, which is widely known for its applications in nuclear energy and weapons. It is one of the three naturally occurring isotopes of uranium and is the only one that is fissile, meaning it can sustain a nuclear chain reaction. This property makes Uranium-235 extremely valuable for nuclear reactors and atomic bombs.
The number 235 refers to its atomic mass, which is the total number of protons and neutrons in the nucleus. In Uranium-235, there are 92 protons, as is typical for all uranium isotopes due to their position in the periodic table. The protons give uranium its chemical character. Alongside the protons, Uranium-235 has 143 neutrons. The distinct number of neutrons results in different physical properties compared to other isotopes.
Uranium-235 is less stable than other isotopes but is significantly more reactive, which is harnessed in various applications. Its ability to undergo fission when struck by a neutron releases a tremendous amount of energy, underlying its critical role in modern nuclear technology.

Uranium-238

Uranium-238 is the most common isotope of uranium in nature, making up over 99% of the uranium found in the Earth's crust. Its name denotes an atomic mass of 238, which consists of both protons and neutrons in the nucleus. Like all uranium isotopes, Uranium-238 contains 92 protons. This consistency in proton number is what defines uranium as an element.
The significant feature of Uranium-238 is its 146 neutrons. These extra neutrons compared to Uranium-235 contribute to its higher atomic mass and make it much more stable than its fissile counterpart. While it can't directly sustain a nuclear chain reaction, Uranium-238 is valuable in nuclear technology through its ability to transform into plutonium-239, another fissile material, under neutron bombardment.
Uranium-238's greater stability and abundance make it a critical component in various applications, including nuclear energy and geologic dating, by analyzing isotope ratios to date rocks and meteorites.

Neutron difference

Understanding the neutron difference between Uranium-235 and Uranium-238 is crucial in comprehending their different properties and applications. As isotopes of the same element, they have identical numbers of protons but vary in their neutron count. This variation leads to their differing atomic masses.
Uranium-238 has three more neutrons than Uranium-235, with 146 neutrons compared to 143 in Uranium-235. This difference is not only numerical but also significant because it affects the isotopes' stability and potential for nuclear reactions. The additional neutrons in Uranium-238 confer greater stability, reducing its chance of undergoing spontaneous fission.
This slight difference in neutron number is central to their roles in nuclear science, with Uranium-235 being preferred for its reactivity in fission-based applications, while Uranium-238 is often utilized for breeding fissile materials like plutonium in reactors.

Subatomic particles

Subatomic particles are the building blocks of atoms and include protons, neutrons, and electrons. Understanding these particles is essential to grasping the properties of isotopes like Uranium-235 and Uranium-238.
Protons carry a positive charge and, along with neutrons, form the nucleus of an atom. Neutrons do not carry any charge and serve to stabilize the nucleus. The number of protons within the nucleus of an atom determines the element—here, all uranium isotopes feature 92 protons.
Electrons are negatively charged particles that orbit the nucleus and balance the positive charge of the protons. However, the term "subatomic particles" generally refers to the particles within the nucleus when discussing isotopes. Understanding the interaction of these particles explains the distinct characteristics and behaviors of different isotopes. For example, it is the different number of neutrons in Uranium-235 and Uranium-238 that leads to their varying atomic masses and nuclear properties.