Question

Calculate the number of neutrons of \({ }^{239} \mathrm{Pu}\)

Short answer

The number of neutrons in \({}^{239} \mathrm{Pu}\) is 145.

Step-by-step solution

Identify the Atomic Mass and Atomic Number

The given isotope is \({}^{239} \mathrm{Pu}\). For plutonium (Pu), the atomic number, which represents the number of protons, is 94, and the atomic mass number given is 239.

Understand the Equation for Neutrons

Neutrons in an atom can be calculated using the equation: \[\text{Number of Neutrons} = \text{Atomic Mass} - \text{Atomic Number}\] where the atomic mass is the sum of protons and neutrons.

Apply the Formula

Insert the values into the equation: \[\text{Number of Neutrons} = 239 - 94\] Calculate the number of neutrons.

Calculate the Number of Neutrons

Perform the subtraction: \[239 - 94 = 145\] Thus, \({}^{239} \mathrm{Pu} \) has 145 neutrons.

Key concepts

Atomic Mass

The atomic mass, also known as the atomic mass number, is crucial in identifying isotopes of a given element. It refers to the total number of protons and neutrons in the nucleus of an atom. Since protons and neutrons have approximately the same mass, atomic mass is almost equal to the mass of the atom in atomic mass units (amu). In isotopic notation, the atomic mass is typically placed at the top left corner, representing the total count of protons and neutrons. For example, in the case of \(^{239} \mathrm{Pu}\), the atomic mass is 239, indicating that plutonium has a combination of 239 protons and neutrons. This number is significant as it helps in calculating other properties such as the number of neutrons, which we'll explore next.

Atomic Number

The atomic number is a defining property of an element, reflected by the number of protons in the nucleus of an atom. This number is paramount because it determines the chemical identity of the element. For plutonium, the atomic number is 94, which means every plutonium atom has 94 protons. This information is also part of the element's symbol in the periodic table, often displayed as the subscript on the left. The atomic number not only identifies the element but also provides the basis for understanding electron configuration, bonding behavior, and placement in the periodic table, highlighting its role in determining chemical properties.

Neutrons

Neutrons are subatomic particles found in the nucleus of an atom, alongside protons. These particles are crucial in providing stability to the atom by offsetting the repulsive forces between positively charged protons. The number of neutrons in an atom can be calculatd with the simple formula: \[\text{Neutrons} = \text{Atomic Mass} - \text{Atomic Number}\]For \(^{239} \mathrm{Pu}\), this means:

• Atomic Mass = 239
• Atomic Number = 94
• Calculation: 239 - 94 = 145

Therefore, \(^{239} \mathrm{Pu}\) has 145 neutrons. Neutrons play a vital role in isotopic variations, resulting in differences in atomic mass while keeping the atomic number unchanged, pertinent in isotopic analysis.

Plutonium Isotope

Plutonium, a heavy element, has several isotopes, which differ due to variations in their atomic mass. Isotopes are variants of the same element that contain the same number of protons but different numbers of neutrons. The specific isotope, \(^{239} \mathrm{Pu}\), refers to plutonium with 94 protons and 145 neutrons, summing up to an atomic mass of 239. Isotopes are significant in both chemical and nuclear applications. For example, \(^{239} \mathrm{Pu}\) is notable for its role in nuclear reactors and weapons, showcasing how variations in neutron number affect an isotope's behavior and use. Understanding isotopic differences is essential in fields like chemistry, physics, and nuclear engineering, emphasizing the variety in atomic nuclei.