Question

Atomic Terminology Practice. a. The most common form of iron has 26 protons and 30 neutrons in its nucleus. State its atomic number, atomic mass number, and number of electrons if it is electrically neutral. b. Consider the following three atoms: Atom 1 has seven protons and eight neutrons; atom 2 has eight protons and seven neutrons; atom 3 has eight protons and eight neutrons. Which two are isotopes of the same element? c. Consider fluorine atoms with nine protons and ten neutrons. What are the atomic number and atomic mass number of this fluorine? Suppose we could add a proton to this fluorine nucleus. Would the result still be fluorine? Explain. What if we added a neutron to the fluorine nucleus? d. The most common isotope of uranium is \(^{238} \mathrm{U}\), but the form used in nuclear bombs and nuclear power plants is \(^{235} \mathrm{U}\) Given that uranium has atomic number \(92,\) how many neutrons are in each of these two isotopes of uranium?

Short answer

a. Atomic number 26, mass number 56, 26 electrons. b. Atom 2 and Atom 3. c. Atomic number 9, mass number 19; adding a proton gives neon, a neutron gives a fluorine isotope. d. 146 neutrons in \(^{238}\text{U}\), 143 in \(^{235}\text{U}\).

Step-by-step solution

Atomic Number and Atomic Mass Number of Iron

The atomic number is the number of protons in an atom's nucleus. Thus, the atomic number of the iron atom is 26. The atomic mass number is the total number of protons and neutrons. For iron, this is calculated as 26 protons + 30 neutrons = 56. Since the atom is electrically neutral, it must have the same number of electrons as protons, which is 26. - **Atomic Number:** 26 - **Atomic Mass Number:** 56 - **Number of Electrons:** 26

Identifying Isotopes

Isotopes are atoms with the same number of protons but different numbers of neutrons. Comparing the atoms: - Atom 1 has 7 protons and 8 neutrons. - Atom 2 has 8 protons and 7 neutrons. - Atom 3 has 8 protons and 8 neutrons. Both Atom 2 and Atom 3 have the same number of protons (8), which means they are isotopes of the element oxygen. Thus, Atom 2 and Atom 3 are isotopes of the same element. - **Isotopes:** Atom 2 and Atom 3 (Oxygen)

Fluorine Atomic Details and Hypotheticals

For fluorine with 9 protons and 10 neutrons: - The atomic number is the number of protons, which is 9. - The atomic mass number is 9 protons + 10 neutrons = 19. If a proton is added, it would become an atom of a different element, neon, since the element is defined by the number of protons. Adding a neutron will not change the element; it will create an isotope of fluorine. - **Fluorine Atomic Number:** 9 - **Fluorine Atomic Mass Number:** 19 - **Adding a Proton yields:** Neon - **Adding a Neutron yields:** Isotope of Fluorine

Neutron Calculation for Uranium Isotopes

For uranium with atomic number 92 (92 protons):- For \(^{238} ext{U}\), the atomic mass number is 238. Neutrons = Atomic mass number - Atomic number = 238 - 92 = 146.- For \(^{235} ext{U}\), the atomic mass number is 235. Neutrons = 235 - 92 = 143.- **Neutrons in \(^{238} ext{U}\):** 146- **Neutrons in \(^{235} ext{U}\):** 143

Key concepts

Atomic Number

The atomic number is a fundamental concept in atomic physics and chemistry. It essentially defines what element an atom is, by indicating the number of protons present in the nucleus. For instance, the atomic number of iron is 26 because it contains 26 protons in its nucleus. This number distinguishes iron from other elements.
Additionally, in a neutral atom, the atomic number also tells us the number of electrons outside the nucleus, balancing the positive charge of the protons. So, in a neutral iron atom, there are 26 electrons.
Understanding the atomic number helps clarify why different elements behave differently and have unique properties. It serves as the identifier of an element in the periodic table.

Isotopes

Isotopes are fascinating variations of elements that have the same number of protons but different numbers of neutrons. This means isotopes are atoms of the same element, sharing the same atomic number but differing in atomic mass.
For example, let’s consider oxygen. Atoms of oxygen always have 8 protons, but they can have different numbers of neutrons. Atom 2 and Atom 3, both have 8 protons, making them isotopes of oxygen. Atom 2 has 7 neutrons, and Atom 3 has 8 neutrons.
Isotopes can have distinct properties. While their chemical behavior remains largely identical, their physical properties, such as stability, can vary greatly. This idea is crucial in fields like radiochemistry and medical imaging.

Neutrons

Neutrons are uncharged particles found in the nucleus of an atom, playing a key role in the identity of isotopes. They contribute to the atomic mass of an atom, along with protons, without affecting the atomic number. For instance, uranium isotopes can be distinguished by the number of neutrons they have.
Taking uranium as an example, with an atomic number of 92, isotopes like \(^{238}\text{U}\) have 146 neutrons, while \(^{235}\text{U}\) has 143 neutrons.
Neutrons are vital because their variations can lead to instability in isotopes, leading to radioactive decay. This property is instrumental in radiometric dating, nuclear reactors, and in medical applications.

Electrons

Electrons, being negatively charged particles, orbit the nucleus and play a critical role in chemical reactions and bonding. Their arrangement and number in a neutral atom are equal to the number of protons, balancing the atomic charge. Thus, for an atom like iron, which has 26 protons, there are also 26 electrons when it is neutral.
Electrons are organized in various energy levels or shells, and their configuration determines how an atom will interact with others. This property is fundamental to the structure of molecules and the behavior of materials.
Moreover, the loss or gain of electrons leads to the formation of ions, resulting in ionic bonds, a key concept in chemistry that explains the formation of many substances around us.