Problem 39 - General Chemistry: Principles and Modern Applications

Question

Americium-241 is a radioactive isotope that is used in high-precision gas and smoke detectors. How many neutrons, protons, and electrons are there in an atom of americium-241?

Step-by-Step Solution

Answer

An atom of Americium-241 contains 95 protons, 95 electrons, and 146 neutrons.

Step 1: Identify the Atomic Number

The atomic number of an element corresponds to the number of protons it has in its nucleus. Americium is the element with atomic number 95, which means it has 95 protons.

Step 2: Validate the Neutrality of the Atom

In a neutral atom, the number of electrons equals the number of protons as to balance out the charges. Therefore, a neutral Americium atom also consists of 95 electrons.

Step 3: Find Out the Number of Neutrons

The mass number of Americium-241 signifies it has a total of 241 particles in the nucleus, which includes both protons and neutrons. The number of neutrons can be found by subtracting the atomic number from the mass number, i.e., 241 - 95 = 146. Therefore, an atom of Americium-241 contains 146 neutrons.

Key Concepts

Atomic Structure

Atomic structure refers to the organization of protons, neutrons, and electrons within an atom. These subatomic particles together build the identity of individual atoms and consequently, all matter. Here are the key components:

• **Protons**: These are positively charged particles found in the nucleus of an atom. They determine the atomic number of an element, which is unique to every element. For instance, Americium has an atomic number of 95 because it has 95 protons.


• **Neutrons**: These are neutral particles, meaning they have no charge and exist in the nucleus alongside protons. Neutrons help to bind protons together within the nucleus and affect the atomic mass of an element.


• **Electrons**: These negatively charged particles orbit the nucleus. In a neutral atom, the number of electrons equals the number of protons, balancing the overall charge. So, Americium-241 also has 95 electrons.

Understanding atomic structure helps explain why elements have their specific chemical and physical properties. This structure defines how atoms bond with one another and react chemically.

Radioactive Isotopes

Radioactive isotopes are atoms with unstable nuclei that spontaneously release energy in the form of radiation. This occurs as the atoms seek stability by shedding excess atomic energy. Here's an overview of radioactive isotopes:

• **Nature of Radioactivity**: It involves the transformation of an atom's nucleus. Unstable isotopes naturally undergo changes over time, emitting particles or electromagnetic radiation through radioactive decay.


• **Americium-241**: Americium-241 is a popular radioactive isotope used in devices like smoke detectors due to its long half-life of about 432 years. Its stability over time makes it ideal for continuous use in safety equipment.


• **Usage and Safety**: While useful, radioactive isotopes like Americium-241 must be handled carefully due to their radiation. Proper precautions ensure that their benefits outweigh the potential risks.

The understanding of radioactive isotopes is crucial not just for scientific exploration but also for practical applications in medicine, industry, and environmental monitoring.

Neutron Calculation

Calculating the number of neutrons in an atom is a straightforward but essential task in understanding atomic composition. Neutrons in an atom can be calculated using the formula:\[\text{Number of Neutrons} = \text{Mass Number} - \text{Atomic Number}\]Let's break it down with Americium-241:

• **Mass Number**: This is the sum of protons and neutrons in the nucleus of an atom. For Americium-241, the mass number is 241.


• **Atomic Number**: This is the number of protons, defining the element. Americium has an atomic number of 95.


• **Neutron Calculation**: Subtract the atomic number from the mass number: \[241 - 95 = 146\]This means that Americium-241 has 146 neutrons.

Understanding neutron calculation is vital for many scientific fields, including chemistry and nuclear physics, as it determines an atom's isotopic identity and stability.