Problem 21 - Chemistry The Molecular Science

Question

The artificial radioactive element technetium is used in many medical studies. Give the number of electrons, protons, and neutrons in an atom of technetium-99.

Step-by-Step Solution

Answer

Technetium-99 has 43 electrons, 43 protons, and 56 neutrons.

Step 1: Identify the Element

Technetium is a chemical element with the symbol 'Tc' and atomic number 43, which means every atom of technetium contains 43 protons.

Step 2: Determine Number of Protons

Since the atomic number of technetium is 43, the atom contains 43 protons. The atomic number corresponds to the number of protons in the nucleus.

Step 3: Determine Number of Electrons

For a neutral atom, the number of electrons equals the number of protons to balance the electric charge. Therefore, a neutral technetium atom has 43 electrons.

Step 4: Calculate Number of Neutrons

The mass number of an isotope, like technetium-99, is given as 99. This mass number is the sum of protons and neutrons. Calculate the number of neutrons by subtracting the number of protons from the mass number: \( 99 - 43 = 56 \). Hence, a technetium-99 atom has 56 neutrons.

Key Concepts

Atomic Structure

Understanding atomic structure is key to identifying the components of an atom such as technetium-99, which is an artificial radioactive element. Atoms are the building blocks of matter and consist of three main particles: protons, neutrons, and electrons. These particles are organized in a specific way:

• Protons: These positively charged particles reside in the nucleus of an atom. The number of protons is unique for each element and is referred to as the atomic number.
• Neutrons: Neutron numbers can vary even among atoms of the same element, leading to different isotopes. They are neutral particles that also inhabit the nucleus.
• Electrons: Negatively charged particles that orbit the nucleus in electron shells.

For technetium, with an atomic number of 43, the structure of its atom consists of 43 protons and typically, in a neutral atom, 43 electrons. The unique arrangement of these particles determines an element’s chemical properties and its position in the periodic table.

Neutron Calculation

Neutron calculation in any isotope, like technetium-99, involves using its mass number. The mass number represents the total number of protons and neutrons in an atom's nucleus. To find the number of neutrons, you subtract the number of protons from the mass number. This is a relatively straightforward process:

• First, identify the mass number of the isotope, which in the case of technetium-99 is 99.
• Next, identify the atomic number, which is the number of protons in the nucleus. For technetium, this is 43.
• Subtract the atomic number from the mass number: \( 99 - 43 = 56 \).

Therefore, technetium-99 has 56 neutrons. This process is essential for distinguishing between different isotopes of the same element.

Radioactive Isotopes

Radioactive isotopes, or radioisotopes, are variants of elements that have an unstable nucleus. This instability leads to the emission of radiation as the isotope decays to a more stable form. Technetium-99 is a prime example and has applications in various fields, most notably in medical diagnostics.

• Technetium-99m, a metastable nuclear isomer of Tc-99, is widely used in imaging studies because it emits gamma rays.
• The presence of an additional 56 neutrons over the typical number of protons contributes to this instability.
• Radioisotopes can transform into a different element once the unstable nucleus releases energy and particles during decay.

Understanding radioactive isotopes allows scientists and medical professionals to harness their properties for beneficial uses, such as targeting cancer cells with radiation therapy or tracing pathways of substances in biological systems.