Problem 94 - Chemistry: The Central Science

Question

The element oxygen has three naturally occurring isotopes, with 8,9 , and 10 neutrons in the nucleus, respectively. (a) Write the full chemical symbols for these three isotopes. (b) Describe the similarities and differences between the three kinds of atoms of oxygen.

Step-by-Step Solution

Answer

(a) The full chemical symbols for the three oxygen isotopes are: \(_8^{16}\)O, \(_8^{17}\)O, and \(_8^{18}\)O. (b) Similarities: 1. All isotopes have the same atomic number (8) and chemical properties. 2. They share the same electron configuration, resulting in similar chemical behavior. Differences: 1. They have different mass numbers due to varying numbers of neutrons (8, 9, and 10). 2. Atomic masses differ, affecting the isotopes' physical properties. 3. They have distinct nuclear properties, such as stability and decay rates.

Step 1: a) Full chemical symbols

To write the full chemical symbols for the three oxygen isotopes, we need to know the element's symbol and atomic number. Oxygen has the symbol 'O' and an atomic number of 8 (which means it has 8 protons). We're given that the isotopes have 8, 9, and 10 neutrons, so we can now calculate their mass numbers as follows: 1. For the isotope with 8 neutrons: mass number = 8 protons + 8 neutrons = 16 2. For the isotope with 9 neutrons: mass number = 8 protons + 9 neutrons = 17 3. For the isotope with 10 neutrons: mass number = 8 protons + 10 neutrons = 18 Now we can write the full chemical symbols for these isotopes, which include the element symbol, atomic number (subscript), and mass number (superscript): 1. \(_8^{16}\)O 2. \(_8^{17}\)O 3. \(_8^{18}\)O

Step 2: b) Similarities and differences

Now we'll describe the similarities and differences between these oxygen isotopes. Similarities: 1. All three isotopes have the same atomic number (8), meaning they all have 8 protons in their nucleus. 2. They all share the same chemical properties, as these properties are determined by the number of protons and electrons, which are equal in all three cases. 3. All three isotopes have the same electron configuration, so they form similar chemical bonds and exhibit the same chemical behavior. Differences: 1. They have different mass numbers, as their number of neutrons varies (8, 9, and 10). 2. Due to the different mass numbers, they have different atomic masses, which can affect the physical properties of the isotopes (e.g., density, boiling/melting points). 3. These isotopes can be distinguished by their different nuclear properties (e.g., stability, abundance, decay rates). For example, \(_{8}^{18}\)O is stable, while \(_{8}^{17}\)O has a much shorter half-life, making it less stable.

Key Concepts

Nuclear Properties

The nuclear properties of isotopes refer to characteristics that depend on the composition and arrangement of particles within the nucleus. Isotopes of an element have the same number of protons but differ in their number of neutrons. Oxygen has three isotopes with 8, 9, and 10 neutrons, respectively. These different neutron counts result in varying nuclear properties, such as:

• Stability: Some isotopes are stable, while others might be radioactive, meaning they can decay over time. For instance, \(_{8}^{18}\)O is stable.
• Decay Rates: The rate at which an unstable isotope decays can differ greatly. Isotopes with more neutrons might have higher instability.
• Abundance: Naturally occurring isotopes might vary in abundance, with more stable isotopes being usually more common.

These nuclear properties influence the practical applications and behaviors of each isotope in scientific and industrial settings.

Atomic Number

The atomic number is a fundamental concept for understanding elements and isotopes. It represents the number of protons in the nucleus of an atom. For oxygen, the atomic number is always 8. This means every oxygen atom has 8 protons. The atomic number determines the element's identity and its position on the periodic table. As a result, regardless of the number of neutrons, all isotopes of oxygen will possess the same atomic number:

• The atomic number is crucial in defining chemical properties, as it also indicates the number of electrons in a neutral atom.
• Since all oxygen isotopes share the atomic number 8, they all exhibit similar chemical behaviors.

Thus, the atomic number is central to an element's fundamental characteristics.

Chemical Properties

Chemical properties of an element involve its ability to engage in chemical reactions and bond with other elements. These properties are mainly determined by the atom's electronic configuration, which is tied to the number of protons, or the atomic number.Since all isotopes of oxygen (\(_{8}^{16}\)O, \(_{8}^{17}\)O, \(_{8}^{18}\)O) share the same atomic number, they have identical electronic configurations. This results in all oxygen isotopes having the same:

• Reactivity: Oxygen isotopes react in a similar manner chemically due to their identical configuration of electrons.
• Bonding: They form similar bonds with other elements, producing compounds like water (H\(_{2}\)O) or carbon dioxide (CO\(_{2}\)).

Thus, chemical properties remain consistent across isotopes due to their shared atomic configuration.

Mass Number

The mass number of an atom is the sum of its protons and neutrons. Unlike the atomic number, the mass number can vary among isotopes of the same element.For the isotopes of oxygen:

• \(_{8}^{16}\)O has a mass number of 16 (8 protons + 8 neutrons).
• \(_{8}^{17}\)O has a mass number of 17 (8 protons + 9 neutrons).
• \(_{8}^{18}\)O has a mass number of 18 (8 protons + 10 neutrons).

The differences in mass number lead to variations in properties such as atomic mass, which can affect physical properties like density and melting points. However, these differences do not alter the chemical properties of the isotopes. Understanding mass numbers is key in identifying and differentiating between the physical attributes of isotopes.