Problem 124 - Introductory Chemistry Atoms First

Question

There are three isotopes of hydrogen-protium, deuterium, and tritium. Protium contains one proton and no neutrons. Deuterium contains one more neutron than protium, and tritium contains one more neutron than deuterium. For each isotope, give the atomic number, mass number, number of protons/ neutrons/electrons, and full atomic symbol.

Step-by-Step Solution

Answer

Protium: Atomic Number = 1, Mass Number = 1, Protons = 1, Neutrons = 0, Electrons = 1, Full Atomic Symbol = \(_{1}^{1}H\). Deuterium: Atomic Number = 1, Mass Number = 2, Protons = 1, Neutrons = 1, Electrons = 1, Full Atomic Symbol = \(_{1}^{2}H\). Tritium: Atomic Number = 1, Mass Number = 3, Protons = 1, Neutrons = 2, Electrons = 1, Full Atomic Symbol = \(_{1}^{3}H\).

Step 1: Understand the basic atomic properties

Before solving the problem, it's essential to know what atomic number, mass number, and atomic symbols represent. - Atomic number (Z): It's the number of protons in an atom's nucleus. It determines an element's identity. - Mass number (A): It's the sum of protons and neutrons in an atom's nucleus. - Atomic symbol: An element is represented by \(_{Z}^{A}X\), where X is the chemical symbol of the element, such as H for hydrogen.

Step 2: Analyzing Protium

Protium contains one proton and no neutrons. - Atomic number (Z): Since it's a hydrogen isotope with 1 proton, its atomic number is 1. - Mass number (A): With only 1 proton and 0 neutrons, its mass number is also 1. - Protons: There is 1 proton. - Neutrons: There are 0 neutrons. - Electrons: Since hydrogen has no charge, it has 1 electron. - Full atomic symbol: \(_{1}^{1}H\).

Step 3: Analyzing Deuterium

Deuterium, another hydrogen isotope, contains one more neutron than protium. - Atomic number (Z): It has 1 proton, so its atomic number is 1. - Mass number (A): Deuterium has 1 proton and 1 neutron, so its mass number is 2. - Protons: There is 1 proton. - Neutrons: There is 1 neutron. - Electrons: Again, since it's an isotope of hydrogen, it has 1 electron. - Full atomic symbol: \(_{1}^{2}H\).

Step 4: Analyzing Tritium

Tritium, the third hydrogen isotope, contains one more neutron than deuterium. - Atomic number (Z): As hydrogen isotope with 1 proton, its atomic number is 1. - Mass number (A): Tritium has 1 proton and 2 neutrons, so its mass number is 3. - Protons: There is 1 proton. - Neutrons: There are 2 neutrons. - Electrons: As a hydrogen isotope, it has 1 electron. - Full atomic symbol: \(_{1}^{3}H\). Results: - Protium: Atomic Number = 1, Mass Number = 1, Protons = 1, Neutrons = 0, Electrons = 1, Full Atomic Symbol = \(_{1}^{1}H\). - Deuterium: Atomic Number = 1, Mass Number = 2, Protons = 1, Neutrons = 1, Electrons = 1, Full Atomic Symbol = \(_{1}^{2}H\). - Tritium: Atomic Number = 1, Mass Number = 3, Protons = 1, Neutrons = 2, Electrons = 1, Full Atomic Symbol = \(_{1}^{3}H\).

Key Concepts

Atomic Number

The atomic number, often denoted by the letter Z, is a fundamental characteristic of an element that defines its identity. It represents the number of protons in the nucleus of an atom. Since protons carry a positive charge and each element has a unique number of protons, the atomic number also determines the electric charge of the nucleus. For hydrogen isotope, whether it's protium, deuterium, or tritium, the atomic number remains constant at 1, since each isotope has only one proton in its nucleus.

This simple yet crucial concept helps to categorize elements in the periodic table and is the basis for determining the arrangement of electrons surrounding the nucleus. For students, remembering that the atomic number is equal to the number of protons is key to identifying any element.

Mass Number

Mass number, represented by the letter A, is the sum total of protons and neutrons in an atom's nucleus. Unlike the atomic number, the mass number varies among isotopes of the same element since they can have different numbers of neutrons. Hydrogen, for example, has three isotopes - protium with a mass number of 1 (1 proton + 0 neutrons), deuterium with a mass number of 2 (1 proton + 1 neutron), and tritium with a mass number of 3 (1 proton + 2 neutrons).

Understanding that the proton plus neutron combination gives the atom most of its mass allows students to grasp why isotopes of the same element have different mass numbers despite having the same atomic number.

Atomic Symbol

The atomic symbol is a unique designation of each element based on the international standard of chemical nomenclature. Written as \( _{Z}^{A}X \), the symbol combines the element's chemical symbol (X), atomic number (Z), and mass number (A). For instance, the atomic symbols for protium, deuterium, and tritium are \( _{1}^{1}H \), \( _{1}^{2}H \), and \( _{1}^{3}H \) respectively.

This notation succinctly communicates an element's identity along with the specific isotope information in a compact form. Visually understanding how to read and interpret atomic symbols reinforces a student's comprehension of atomic properties and isotopic variations.

Neutrons in Isotopes

Neutrons play a pivotal role in the diversity of isotopes, as they contribute to the mass number without affecting the atomic number. Isotopes are variants of a particular chemical element that differ in neutron number, while their number of protons, which determine the atomic number, remains unchanged. Neutrons provide stability to the nucleus, and variations in their number can lead to stable or radioactive isotopes.

For example, in hydrogen isotopes, protium has zero neutrons, deuterium has one, and tritium has two. This influences both their nuclear properties and mass, but not their chemical behavior. Students often find it easier to recognize isotopes by focusing on the neutron count, especially since this is a distinct difference between isotopes of the same element.

Protium

Protium (\( _{1}^{1}H \) or simply H) is the most common hydrogen isotope, characterized by having one proton and, uniquely, no neutrons in its nucleus. It's the lightest type of hydrogen and makes up over 99.98% of natural hydrogen found in the universe. Its atomic number is 1, and so is its mass number.

Since it doesn't contain neutrons, it often serves as a base comparison point for understanding isotopes. Having a grasp of protium is essential for students as it underpins fundamental principles of atomic structure and defines the basic building block for the hydrogen element.

Deuterium

Deuterium, or heavy hydrogen, is denoted as \( _{1}^{2}H \) or D, and it has one neutron in addition to the single proton found in protium. This gives deuterium a mass number of 2. It's a stable hydrogen isotope that exists in very small amounts in nature, approximately 0.0156% of natural hydrogen.

Deuterium plays a key role in various scientific fields, including nuclear fusion research and tracing chemical pathways in metabolic studies. For educational purposes, deuterium can be used to illustrate the impact of neutrons on atom mass and the existence of natural isotopic variation.

Tritium

Tritium (\( _{1}^{3}H \) or T) is the third and least abundant naturally occurring isotope of hydrogen, and it stands out by having two neutrons in its nucleus along with the single proton, leading to a mass number of 3. Tritium is radioactive and emits low-energy beta particles during decay.

Despite its rarity and radioactivity, tritium is significant in research, particularly in self-powered lighting and nuclear fusion experiments. When learning about tritium, students engage with the concepts of radioactivity and its applications, providing a deeper understanding of isotopic properties and their practical use in various technologies.