Question

In the polyatomic ion \(\mathrm{T} \mathrm{c} \mathrm{O}_{4}^{-}, \mathrm{T} \mathrm{c}\) has a hypothetical charge of \(7+\). The \({ }^{99} \mathrm{Tc}\) isotope is used in medicine for imaging purposes. It has a mass of \(98.90625 \mathrm{u}\). Give the number of protons, neutrons, and electrons for a \(\mathrm{Tc}^{7+}\) ion.

Short answer

The technetium isotope Tc-99 has 43 protons, 36 electrons, and 56 neutrons.

Step-by-step solution

Determine the number of protons in Tc

The number of protons in an element is equal to its atomic number. The atomic number of technetium (Tc) is 43, which can be found on the periodic table. Therefore, Tc has 43 protons.

Determine the number of electrons in Tc

In a neutral atom, the number of electrons equals the number of protons. However, for the Tc ion with a charge of 7+, it has lost 7 electrons. Therefore, the number of electrons in Tc is 43 (number of protons) - 7 (charge), which equals 36 electrons.

Determine the number of neutrons in Tc

The number of neutrons can be found by subtracting the atomic number from the atomic mass (rounded to the nearest whole number). The atomic mass of Tc is given as 98.90625 u. Rounding this to the nearest whole number gives 99. Therefore, the number of neutrons is 99 (mass number) - 43 (atomic number), which equals 56 neutrons.

Key concepts

Atomic Number

The atomic number is a fundamental characteristic of an element that determines its position in the periodic table and its chemical properties. It is simply the number of protons found in the nucleus of an atom of that element. Each element has a unique atomic number, making it a handy identifier. For instance, technetium (Tc), a transition metal, has the atomic number 43. This means every atom of technetium contains 43 protons in its nucleus.

Understanding the atomic number is crucial because it not only defines the element but also sheds light on the number of electrons in a neutral atom, which influences the atom's ability to form chemical bonds and its overall reactivity.

Number of Protons

Protons are positively charged particles located within an atom's nucleus. The number of protons in the nucleus is the defining feature of an element and, as mentioned earlier, is equal to the atomic number. In the case of technetium, with an atomic number of 43, we know that there are exactly 43 protons in its nucleus. This permanence in the number of protons is why elements retain their identity, and changing the number of protons effectively changes the element itself. Thus, the stability and identity of an element hinge on the immutable count of protons present.

Number of Neutrons

Neutrons are neutrally charged particles, contributing to the overall mass of an atom but not its charge. The number of neutrons in an atom can vary, even among atoms of the same element, leading to the existence of different isotopes. To find the number of neutrons, we usually subtract the atomic number from the atomic mass number, the latter of which is the sum of protons and neutrons in the nucleus. For technetium-99, we take the rounded atomic mass of 99 and subtract the atomic number (43) to get 56 neutrons.

Number of Electrons

Electrons are negatively charged particles that orbit the nucleus within an atom. In a neutral atom, the number of electrons is equal to the number of protons, negating the positive charge of the nucleus and resulting in no overall charge. However, atoms can lose or gain electrons through various processes, becoming ions. For a technetium ion with a 7+ charge (Tc⁷⁺), this indicates it has 7 fewer electrons than protons. Since technetium has 43 protons, the Tc⁷⁺ ion would have 36 electrons.

Technetium

Technetium is a chemical element with symbol Tc and atomic number 43. It's noteworthy as the lightest element whose isotopes are all radioactive; none are stable other than the fully ionized state. The most commonly used isotope in medicine is technetium-99m. It decays but not instantaneously, making it useful for various diagnostic procedures, such as medical imaging. Despite its instability, technetium's various forms have become critical tools in the field of nuclear medicine.

Isotopes in Medicine

Isotopes play a significant role in the medical field, particularly in the area of diagnostic imaging and treatment. An isotope is a variant of an element that has the same number of protons but a different number of neutrons. This difference can make certain isotopes radioactive, where they emit particles that can be tracked or used to target diseased tissue. Technetium-99m, for instance, is an isotope widely used in medical imaging because of its ideal physical properties. Its relatively short half-life and gamma-ray emission make it perfect for creating clear images of organs, such as the heart or brain, helping physicians in diagnoses and further treatment planning.