Consider an isotope of yttrium, Y-90. This isotope is...

Consider an isotope of yttrium, Y-90. This isotope is incorporated into cancer-seeking antibodies so that the cancer can be irradiated by the yttrium and destroyed. How many neutrons are in (a) twenty-five atoms of yttrium? (b) one nanogram $\left(10^{-9} \mathrm{~g}\right)$ of yttrium?

Consider an isotope of yttrium, Y-90. This isotope is incorporated into cancer-seeking antibodies so that the cancer can be irradiated by the yttrium and destroyed. How many neutrons are in
(a) twenty-five atoms of yttrium?
(b) one nanogram $\left(10^{-9} \mathrm{~g}\right)$ of yttrium?

Key Concepts

Isotopes

Isotopes are atoms of the same element that have the same number of protons but different numbers of neutrons. Their atomic mass is determined by the sum of protons and neutrons in the nucleus, which can affect the physical and nuclear properties of the element.

Atomic Structure

Atomic structure describes how an atom is composed of a nucleus containing protons and neutrons, with electrons orbiting around the nucleus. Understanding the composition of an atom is crucial when calculating properties such as the number of neutrons or conversions between atomic-scale masses and macroscopic amounts.

Neutron Calculation

Neutron calculation involves determining the number of neutrons in an atomic nucleus by subtracting the number of protons (the atomic number) from the mass number of the isotope. This concept is important for understanding nuclear reactions, decay processes, and the properties of different isotopes.

Avogadro's Number

Avogadro's number (approximately 6.022 × 10^23) is a fundamental constant that relates the number of atoms or molecules in a mole of a substance. It is essential for converting between the number of individual atoms and the macroscopic mass of a substance in laboratory calculations.

Unit Conversion and Scientific Notation

Unit conversion and the use of scientific notation are key in chemistry and physics to handle very large or small numbers, such as converting grams to moles or atoms. Mastery of these techniques is crucial for accurately relating extremely small-scale atomic properties to measurable quantities in the lab.

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