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Ch.2 - Atoms, Molecules & Ions
All textbooksMcMurry 8th EditionCh.2 - Atoms, Molecules & IonsProblem 6
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Chapter 2, Problem 6

How many protons, neutrons, and electrons are present in an atom of 2 206Pb? (LO 2.14) (a) 82 protons, 206 neutrons, 82 electrons (b) 124 protons, 82 neutrons, 124 electrons (c) 82 protons, 124 neutrons, 82 electrons (d) 82 protons, 82 neutrons, 124 electrons

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Identify the element from the given symbol: \( ^{206}_{82}\text{Pb} \). The symbol 'Pb' stands for lead.
Determine the number of protons: The atomic number (subscript) is 82, which indicates the number of protons in the atom.
Determine the number of electrons: In a neutral atom, the number of electrons equals the number of protons, so there are 82 electrons.
Calculate the number of neutrons: Subtract the atomic number from the mass number (superscript): \( 206 - 82 = 124 \) neutrons.
Match the calculated numbers of protons, neutrons, and electrons with the given options to find the correct answer.

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Key Concepts

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

Atomic Structure

An atom consists of three primary subatomic particles: protons, neutrons, and electrons. Protons are positively charged and reside in the nucleus, while neutrons are neutral particles also found in the nucleus. Electrons are negatively charged and orbit the nucleus in electron shells. The number of protons defines the element, while the total number of protons and neutrons gives the atomic mass.
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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. For example, the notation ²⁰⁶Pb indicates lead with an atomic mass of 206, which means it has 82 protons (as lead's atomic number is 82) and 124 neutrons (206 - 82 = 124). Understanding isotopes is crucial for determining the composition of an atom.
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Charge Balance

In a neutral atom, the number of electrons equals the number of protons, balancing the overall charge. This balance is essential for the stability of the atom. In the case of ²⁰⁶Pb, with 82 protons, there are also 82 electrons, ensuring that the atom is electrically neutral. Recognizing this relationship helps in identifying the correct number of each subatomic particle.
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Related Practice
Textbook Question
Which description of an element is incorrectly matched with its location in the periodic table? (LO 2.5–2.6)

(a) Element 3—An element in the transition metal group that is a good conductor of electricity. (b) Element 2—An element that is in the halogen group and does not conduct electricity. (c) Element 4—An element in alkali metal group that is found in its pure form in nature. (d) Element 1—An element that is a solid at room tempera-ture, brittle, and a poor conductor of electricity.
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Textbook Question
A compound containing sulfur and fluorine contains 8.00 g of S and 9.50 g of F. Which combination of S and F masses represents a different compound that obeys the Law of Mul-tiple Proportions? (LO 2.8) (a) 32.0 g of S and 38.0 g of F (b) 4.00 g of S and 4.75 g of F (c) 8.00 g of S and 10.5 g of F (d) 16.0 g of S and 57.0 g of F
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Textbook Question
Which experiment and subsequent observation led to the discovery that atoms contain negatively charged particles, now known as electrons? (LO 2.10–2.12) (a) Oil is sprayed into a chamber and the speed at which the oil droplets fall is measured with and without an applied voltage. X rays in the chamber knock electrons out of air molecules. The electrons stick to the oil pro-ducing an overall negative charge on the drops. Adjusting the voltage changes the speed at which the negatively charged oil droplets fall. (b) When a high voltage is applied across metal electrodes at opposite ends of a sealed glass tube, a cathode ray is produced. The cathode ray is repelled by a negatively charged plate. (c) A radioactive substance emits alpha particles, which are directed at a thin gold foil. Most of the alpha par-ticles pass through the foil, but a few alpha particles are slightly deflected and some even bounce back toward the radioactive source. (d) The mass of different elements in a pure chemical com-pound are measured. Different samples of the compound always contains the same proportion of elements by mass.
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Textbook Question
What is the atomic weight of an element that consists of two naturally occurring isotopes? The first isotope has a mass of 84.911 and an abundance of 72.17% and the second isotope has a mass of 86.909 and an abundance of 27.83%. (LO 2.15) (a) 85.47 (b) 86.35 (c) 85.91 (d) 85.17
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Textbook Question
Which sample has the greatest mass? (LO 2.16) (a) 5.5 mol of C (b) 2.1 mol of S (c) 4.2 mol of Be (d) 0.52 mol of Ag
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Textbook Question
How many atoms are present in 1.2 g of gold? (LO 2.16) (a) 2.5 * 1021 (b) 1.4 * 1026 (c) 7.2 * 1023 (d) 3.7 * 1021
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