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Ch.4 Atoms and Elements
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 13th Edition
Timberlake13th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9780134421353Not the one you use?Change textbook
Chapter 4, Problem 81a

Consider the following atoms in which X represents the chemical symbol of the element:
168X 169X 1810X 178X 188X
a. What atoms have the same number of protons?

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1
Step 1: Understand the notation used for the atoms. The subscript (bottom number) represents the atomic number, which is the number of protons in the atom. The superscript (top number) represents the mass number, which is the sum of protons and neutrons.
Step 2: Identify the atomic numbers for each atom in the image. For example, ⁷⁵₃₃X has an atomic number of 33, meaning it has 33 protons. Similarly, ⁷⁹₃₄X has an atomic number of 34, meaning it has 34 protons.
Step 3: Compare the atomic numbers of the atoms to determine which ones have the same number of protons. Atoms with the same atomic number are isotopes of the same element.
Step 4: From the image, identify the atoms with the same atomic number. For instance, ⁷⁵₃₃X, ⁷⁸₃₃X, and ⁷⁷₃₃X all have an atomic number of 33, meaning they have the same number of protons.
Step 5: Conclude that the atoms with the same number of protons are isotopes of the same element, and list them accordingly.

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Key Concepts

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

Atomic Number

The atomic number of an element is defined as the number of protons in the nucleus of an atom. It uniquely identifies a chemical element and determines its position in the periodic table. In the context of isotopes, atoms with the same atomic number belong to the same element, regardless of their differing atomic masses.
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Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons, resulting in different atomic masses. For example, the isotopes of element X in the question share the same atomic number but differ in their mass numbers, indicating variations in their neutron count.
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Mass Number

The mass number of an atom is the total number of protons and neutrons in its nucleus. It is represented as the superscript in the notation of an isotope (e.g., ¹⁶₈X). Understanding mass numbers is crucial for distinguishing between different isotopes of the same element, as they can have significant differences in stability and behavior in chemical reactions.
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