Question

Determine the atomic number and mass number for each isotope. (a) the hydrogen isotope with 2 neutrons (b) the chromium isotope with 28 neutrons (c) the calcium isotope with 22 neutrons (d) the tantalum isotope with 109 neutrons

Short answer

Atomic numbers and mass numbers: (a) Hydrogen isotope: Atomic number 1, Mass number 3. (b) Chromium isotope: Atomic number 24, Mass number 52. (c) Calcium isotope: Atomic number 20, Mass number 42. (d) Tantalum isotope: Atomic number 73, Mass number 182.

Step-by-step solution

Identify Hydrogen Isotope With 2 Neutrons

The atomic number of hydrogen is 1, which means it has 1 proton. The mass number is the total number of protons and neutrons in the nucleus. For hydrogen with 2 neutrons, the mass number is 1 (proton) + 2 (neutrons) = 3.

Identify Chromium Isotope With 28 Neutrons

The atomic number of chromium is 24, indicating it has 24 protons. The mass number is found by summing the number of protons and neutrons. For chromium with 28 neutrons, the mass number is 24 (protons) + 28 (neutrons) = 52.

Identify Calcium Isotope With 22 Neutrons

The atomic number of calcium is 20, so it has 20 protons. To find its mass number, we add the number of protons to the number of neutrons. For calcium with 22 neutrons, the mass number is 20 (protons) + 22 (neutrons) = 42.

Identify Tantalum Isotope With 109 Neutrons

The atomic number of tantalum is 73, which corresponds to its number of protons. The mass number is calculated by adding the number of protons to the number of neutrons. With 109 neutrons, the mass number for tantalum is 73 (protons) + 109 (neutrons) = 182.

Key concepts

Isotopes

Isotopes are variations of elements that have the same number of protons but different numbers of neutrons within their nuclei. This difference in neutron count does not affect the chemical properties of an element, which are determined by the number of protons (atomic number), but it does affect the atomic mass.

For example, in the exercise provided, hydrogen normally has one proton and no neutrons, but a hydrogen isotope with two neutrons, known as deuterium, still behaves chemically like hydrogen while having a greater mass number. Therefore, understanding isotopes is crucial when dealing with nuclear reactions and processes, as the variance in neutron numbers can lead to various isotopes undergoing different rates of decay, being used as tracers in medical applications, or being employed as fuel in nuclear reactors.

Protons and Neutrons

Protons and neutrons reside in the nucleus of an atom and are collectively known as nucleons. The number of protons, the atomic number, defines the identity of an element, whereas neutrons play a key role in providing stability to the nucleus.

The mass number of an atom, illustrated in the exercise solutions, is the total count of protons and neutrons. Protons carry a positive charge, and their number must equal that of the negatively charged electrons for an atom to be neutral. Neutrons, having no charge, add mass to the nucleus and can influence the stability of an atom without changing its chemical behavior. Thus, protons govern the chemical characteristics, while neutrons are vital in nuclear phenomena.

Nuclear Chemistry

Nuclear chemistry focuses on the reactions that take place within the nucleus of an atom, such as radioactive decay, fission, and fusion. These processes often involve changes in the number of protons and/or neutrons, leading to the transformation of elements.

Understanding atomic number and mass number is paramount in nuclear chemistry, as they are used to predict the behavior of isotopes in nuclear reactions. Nuclear reactions can release or absorb vast amounts of energy, which can be harnessed for power generation, or can be utilized in medical treatments and imaging techniques. Nuclear chemistry also explores the creation of new elements and isotopes through synthetic methods, emphasizing the stability and decay patterns of different nuclei.

Periodic Table Elements

The periodic table is a chart that organizes elements by increasing atomic number, which reflects the number of protons in an element's nucleus. Each element on the table is represented by a unique symbol, along with its atomic number and average atomic mass.

The arrangement of the table highlights periodic trends in properties, such as electronegativity and ionization energy, and shows the grouping of elements with similar chemical characteristics into families, such as the noble gases or the alkali metals. Information provided by the exercise solutions can help students navigate the periodic table, as one can locate an element by its proton count, while variations in atomic mass on the table often indicate the presence of isotopes.