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Chapter 2: Problem 66

What number of protons and neutrons are contained in the nucleus of each of the following atoms? Assuming each atom is uncharged, what number of electrons are present? a. \(^{235}_{92} \mathrm{U}\) b. \(_{13}^{27} \mathrm{Al}\) c. \(_{26}^{57} \mathrm{Fe}\) d. \(_{82}^{208} \mathrm{Pb}\) e. \(_{37}^{86} \mathrm{Rb}\) f. \(_{20}^{41} \mathrm{Ca}\)

Short Answer

Expert verified
a. 92 protons, 143 neutrons, 92 electrons b. 13 protons, 14 neutrons, 13 electrons c. 26 protons, 31 neutrons, 26 electrons d. 82 protons, 126 neutrons, 82 electrons e. 37 protons, 49 neutrons, 37 electrons f. 20 protons, 21 neutrons, 20 electrons

Step by step solution

01

a. \(^{235}_{92} \mathrm{U}\)#

For Uranium-235, the atomic number Z is 92, which means there are 92 protons. The mass number A is 235. To find the number of neutrons, subtract the atomic number Z from the mass number A: 235 - 92 = 143 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 92 electrons.
02

b. \(_{13}^{27} \mathrm{Al}\)#

For Aluminum-27, the atomic number Z is 13, which means there are 13 protons. The mass number A is 27. To find the number of neutrons, subtract the atomic number Z from the mass number A: 27 - 13 = 14 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 13 electrons.
03

c. \(_{26}^{57} \mathrm{Fe}\)#

For Iron-57, the atomic number Z is 26, which means there are 26 protons. The mass number A is 57. To find the number of neutrons, subtract the atomic number Z from the mass number A: 57 - 26 = 31 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 26 electrons.
04

d. \(_{82}^{208} \mathrm{Pb}\)#

For Lead-208, the atomic number Z is 82, which means there are 82 protons. The mass number A is 208. To find the number of neutrons, subtract the atomic number Z from the mass number A: 208 - 82 = 126 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 82 electrons.
05

e. \(_{37}^{86} \mathrm{Rb}\)#

For Rubidium-86, the atomic number Z is 37, which means there are 37 protons. The mass number A is 86. To find the number of neutrons, subtract the atomic number Z from the mass number A: 86 - 37 = 49 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 37 electrons.
06

f. \(_{20}^{41} \mathrm{Ca}\)#

For Calcium-41, the atomic number Z is 20, which means there are 20 protons. The mass number A is 41. To find the number of neutrons, subtract the atomic number Z from the mass number A: 41 - 20 = 21 neutrons. As the atom is uncharged, the number of electrons will be equal to the number of protons, so there are 20 electrons.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Protons
Protons are fundamental particles found in the nucleus of an atom, along with neutrons. Understanding protons helps in determining an element's identity.
  • The number of protons in an atom is referred to as the atomic number, denoted by "Z".
  • Protons carry a positive charge of +1.
  • The number of protons determines an element鈥檚 chemical properties and its position on the periodic table.
For instance, the Uranium atom, represented as \(^{235}_{92} \mathrm{U}\), contains 92 protons. This is consistent across all Uranium isotopes because it defines the element鈥檚 identity.
The concept of isotopes arises because the number of neutrons can vary, but the number of protons in a particular element remains the same. Understanding protons is crucial when you explore chemical reactions, as they ultimately influence an atom's chemical behavior and interaction with other atoms.
Neutrons
Neutrons are neutral particles found in the atom鈥檚 nucleus, playing a key role in the stability of atoms. Although they do not carry a charge, their presence is just as vital as that of protons.
  • Neutrons contribute to the mass of an atom along with protons.
  • The stability of an atom is significantly influenced by the number of neutrons it contains.
  • The number of neutrons is deduced by subtracting the atomic number (protons) from the atomic mass (protons + neutrons), represented by "A".
For example, in the Uranium atom \(^{235}_{92} \mathrm{U}\), the neutron count is calculated as 235 (mass number) minus 92 (protons), resulting in 143 neutrons.
Neutrons act as a sort of "glue" that holds the atomic nucleus together. An imbalance in the neutron-to-proton ratio can lead to instability, resulting in isotopes that might be radioactive. Therefore, a clear grasp of neutrons helps in nuclear chemistry and physics.
Electrons
Electrons are negatively charged particles that orbit the nucleus of an atom, dictating how an atom engages in chemical bonds and reactions.
  • Electrons carry a charge of -1, balancing the positive charge of protons in a neutral atom.
  • They virtually have negligible mass compared to protons and neutrons.
  • In a neutral atom, the number of electrons equals the number of protons, ensuring the atom has no overall charge.
In the case of Uranium-235, as expressed by \(^{235}_{92} \mathrm{U}\), there are 92 electrons in an uncharged state.
Electrons are involved in forming chemical bonds due to their distribution in discrete energy levels or shells around an atom's nucleus. These shells determine the atom鈥檚 ability to engage with other atoms, forming the basis of chemistry. This makes electrons vital for understanding chemical bonding and electron configurations.

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Most popular questions from this chapter

In an experiment it was found that the total charge on an oil drop was \(5.93 \times 10^{-18} \mathrm{C}\) . How many negative charges does the drop contain?

Each of the following compounds has three possible names listed for it. For each compound, what is the correct name and why aren鈥檛 the other names used? a. \(\mathrm{N}_{2} \mathrm{O} :\) nitrogen oxide, nitrogen(1) oxide, dinitrogen monoxide b. \(\mathrm{Cu}_{2} \mathrm{O}\) : copper oxide, copper(1) oxide, dicopper monoxide c. \(\mathrm{Li}_{2} \mathrm{O}\) : lithium oxide, lithium(1) oxide, dilithium monoxide

Indium oxide contains 4.784 \(\mathrm{g}\) of indium for every 1.000 \(\mathrm{g}\) of oxygen. In \(1869,\) when Mendeleev first presented his version of the periodic table, he proposed the formula \(\operatorname{In}_{2} \mathrm{O}_{3}\) for indium oxide. Before that time it was thought that the formula was InO. What values for the atomic mass of indium are obtained using these two formulas? Assume that oxygen has an atomic mass of 16.00 .

A single molecule has a mass of \(7.31 \times 10^{-23}\) g. Provide an example of a real molecule that can have this mass. Assume the elements that make up the molecule are made of light isotopes where the number of protons equals the number of neutrons in the nucleus of each element.

Before an electrocardiogram (ECG) is recorded for a cardiac patient, the ECG leads are usually coated with a moist paste containing sodium chloride. Why is sodium chloride applied to the leads?
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