Determine the number of protons, neutrons, and electrons in the following isotopes that are used in medical diagnoses: (a) atomic number 9, mass number 18, charge of 1- (b) atomic number \(43,\) mass number \(99,\) charge of \(7+\) (c) atomic number 53 , atomic mass number 131 , charge of \(1-\) (d) atomic number 81, atomic mass number 201, charge of 1+ (e) Name the elements in parts (a), (b), (c), and (d).

The atomic number is a fundamental property of every element. It defines the element's identity by indicating the number of protons in the nucleus of an atom. Every atom of a given element has the same atomic number. For instance, if an atom has an atomic number of 9, like the first isotope used in medical diagnoses in our exercise, this means the atom has 9 protons.

Understanding the atomic number is crucial because it not only tells us the number of protons in an atom but also reveals the number of electrons in a neutral atom — which will have an equal number of protons and electrons to balance the positive and negative charges, respectively. In isotopes with a charge, such as those mentioned in the exercise, the number of electrons will differ from the atomic number, influenced by the net charge of the isotope.

The mass number is the total count of protons and neutrons in the atomic nucleus and gives us a sense of an atom's mass. Unlike the atomic number, the mass number does not define the type of element but rather a specific isotope of that element. For isotopes with an atomic number 53 and mass number 131 — as seen in (c) — we understand it to have a sum of 131 protons and neutrons.

It's crucial to distinguish between atomic number and mass number. The former is unique to each element, while the latter can vary even within atoms of the same element, resulting in different isotopes. Isotopes are atoms with the same number of protons but different numbers of neutrons, which can lead to differences in physical properties and behavior, particularly in medical applications.

To calculate the number of neutrons in an isotope, subtract the atomic number from the mass number. The atomic number is the count of protons and the mass number is the sum of protons and neutrons. For example, with an atomic number of 43 and a mass number of 99, the neutrons in the isotope are calculated as follows: 99 (mass number) - 43 (atomic number) = 56 neutrons.

This calculation is essential in characterizing different isotopes of the same element, as variations in neutron count can influence the isotope's stability and its utility in medical diagnostics and treatments.

Determining the number of electrons in an isotope requires paying attention to the atomic number and the charge. In a neutral atom, the number of electrons equals the number of protons (the atomic number). However, if the isotope is charged, this signifies a gain or loss of electrons. A positive charge indicates fewer electrons, while a negative charge means there are more. For instance, if we have an isotope with an atomic number of 81 and a charge of 1+, it implies that one electron has been lost, so the number of electrons is 80, one less than the number of protons.

Correctly calculating the electron count is vital for understanding an isotope's chemical properties and behavior, especially when involved in medical imaging or treatment, as these processes can be affected by the electron configuration.

Each element on the periodic table is assigned a unique atomic number. By identifying the atomic number of an isotope, the element can be determined. For instance, an isotope with an atomic number of 53 corresponds to the element iodine. Knowing how to identify elements is fundamental for chemistry and medical applications since different elements and their isotopes have specific roles in diagnostic procedures.

In medical diagnoses, isotopes are chosen based on the element's behavior and properties in the body. For example, Iodine-131 (atomic number 53, mass number 131) is commonly used in diagnostics and treatment of thyroid conditions. Understanding how to identify elements allows healthcare professionals to select appropriate isotopes for imaging and therapeutic procedures.