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Ch.2 - Atoms, Molecules & Ions
Chapter 2, Problem 105b

How many protons and neutrons are in the nucleus of the following atoms? (b)

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Step 1: Identify the atomic number (Z) and the mass number (A) of the atom. The atomic number is the number of protons in an atom, and it is unique for each element. The mass number is the total number of protons and neutrons in an atom.
Step 2: To find the number of protons, simply look at the atomic number of the atom. The atomic number is usually listed in the periodic table.
Step 3: To find the number of neutrons, subtract the atomic number from the mass number. This is because the mass number is the sum of protons and neutrons, so subtracting the number of protons (atomic number) will give you the number of neutrons.
Step 4: If the atom is an isotope, it may have a different number of neutrons than the most common form of the atom. In this case, you would use the mass number of the specific isotope to calculate the number of neutrons.
Step 5: Remember that the number of protons defines the element. Changing the number of neutrons results in isotopes, which are different forms of the same element. Changing the number of protons changes the element itself.

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Key Concepts

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

Atomic Structure

Atoms consist of a nucleus containing protons and neutrons, surrounded by electrons in orbitals. The number of protons defines the element and its atomic number, while neutrons contribute to the atomic mass and stability of the nucleus.
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Atom Structure

Protons and Neutrons

Protons are positively charged particles found in the nucleus, and their number determines the element's identity. Neutrons are neutral particles that also reside in the nucleus, and they help stabilize the atom by offsetting the repulsive forces between protons.
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Neutron-to-Proton Plot

Isotopes

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. This variation affects the atomic mass and can influence the stability and radioactive properties of the element.
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