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Ch.2 - Atoms & Elements
Tro - Chemistry: A Molecular Approach 4th Edition
Tro4th EditionChemistry: A Molecular ApproachISBN: 9780134112831Not the one you use?Change textbook
All textbooksTro 4th EditionCh.2 - Atoms & ElementsProblem 54
Chapter 2, Problem 54

Determine the number of protons and the number of neutrons in each isotope. a. 4019K b. 22688Ra c. 9943Tc d. 3315P

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Identify the atomic number (Z) and the mass number (A) for each isotope. The atomic number is the subscript and represents the number of protons. The mass number is the superscript and represents the total number of protons and neutrons.
For each isotope, the number of protons is equal to the atomic number (Z).
To find the number of neutrons in each isotope, subtract the atomic number (Z) from the mass number (A). The formula to use is: Number of neutrons = A - Z.
Apply the formula to each isotope: a. For 40 19K, subtract 19 from 40. b. For 226 88Ra, subtract 88 from 226. c. For 99 43Tc, subtract 43 from 99. d. For 33 15P, subtract 15 from 33.
Summarize the results for each isotope, listing the number of protons and the number of neutrons calculated.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This means they share the same atomic number but have different mass numbers. For example, potassium-40 (40 19K) has 19 protons and 21 neutrons, while potassium-39 would have 19 protons and 20 neutrons.
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Atomic Number and Mass Number

The atomic number of an element, represented by the lower number in isotope notation, indicates the number of protons in the nucleus. The mass number, shown as the upper number, is the total count of protons and neutrons. For instance, in 40 19K, the atomic number is 19 (protons), and the mass number is 40, leading to the calculation of neutrons as 40 - 19 = 21.
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Nuclear Composition

The nuclear composition of an atom refers to the arrangement and quantity of protons and neutrons within its nucleus. Understanding this composition is essential for identifying isotopes and their properties. For example, knowing that 226 88Ra has 88 protons allows us to determine it has 138 neutrons (226 - 88 = 138), which is crucial for understanding its stability and behavior in nuclear reactions.
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