Problem 16 - Chemistry and Chemical Reactivity

Question

Radioactive americium-241 is used in household smoke detectors and in bone mineral analysis. Give the number of electrons, protons, and neutrons in an atom of americium-241.

Step-by-Step Solution

Answer

Americium-241 has 95 protons, 95 electrons, and 146 neutrons.

Step 1: Identify Atomic Number

Americium is a chemical element with the symbol Am. The atomic number of americium is 95. This indicates it has 95 protons in its nucleus.

Step 2: Determine Number of Electrons

For a neutral atom, the number of electrons is equal to the number of protons. Therefore, an americium atom will also have 95 electrons.

Step 3: Use Mass Number to Find Neutrons

The isotope americium-241 means the mass number is 241. To find the number of neutrons, subtract the atomic number (protons) from the mass number: 241 - 95 = 146. Thus, it has 146 neutrons.

Key Concepts

Radioactive Isotopes

Radioactive isotopes are atoms that have an unstable nucleus and release energy by emitting radiation. This process is known as radioactive decay. Each radioactive isotope has a unique half-life, which is the time it takes for half of the isotope to decay. Americium-241 is one such radioactive isotope.
It's widely used in household smoke detectors because it emits alpha particles, which help detect smoke by ionizing the air.
This property makes it a crucial element for safety technology, despite its radioactivity. Being a synthetic element, americium does not occur naturally and must be produced in nuclear reactors.

Atomic Number

The atomic number is a fundamental property of an element, indicating the number of protons in its nucleus. It essentially defines what element an atom is.
An element's position on the periodic table is based on this number, starting from hydrogen with an atomic number of 1.

• For americium, the atomic number is 95, which shows it possesses 95 protons.
• This atomic number not only dictates its chemical properties but also ensures its place among the actinides on the periodic table.

The significance of the atomic number is that it also tells us the number of electrons in a neutral atom, dramatically influencing its chemical behavior.

Neutrons

Neutrons are one of the three main subatomic particles found in an atom's nucleus, along with protons. They carry no electric charge, which is why they play a role in stabilizing the nucleus.
To find the number of neutrons in an atom, you subtract its atomic number from its mass number.

• For americium-241, you take its mass number of 241 and subtract the atomic number, 95.
• This calculation reveals that there are 146 neutrons in americium-241.

Neutrons are crucial in holding the nucleus together, especially as the nucleus becomes larger.

Electrons

Electrons are negatively charged particles that orbit the nucleus of an atom. In a neutral atom, the number of electrons equals the number of protons.
This balance ensures that the atom is electrically neutral.

• For an atom like americium, which has 95 protons, there will be 95 electrons.
• These electrons are arranged in energy levels or shells around the nucleus.
• The arrangement and number of electrons determine the atom's chemical properties and reactivity.

Electrons play a pivotal role in chemical bonds and reactions, connecting atoms to form molecules.

Protons

Protons are positively charged particles found in the nucleus of an atom. Alongside neutrons, they contribute to most of the atom's mass.
The number of protons, denoted by the atomic number, is unique to each element and determines its identity.

• In americium-241, there are 95 protons, aligning it with the atomic number of 95.
• The presence of protons gives the nucleus its positive charge, affecting how atoms interact with each other.

Protons are crucial in defining the physical and chemical properties of an element, influencing how it participates in chemical reactions.