Atomic Number and Mass Number
The revelation of subatomic particles gave a ton of information about the properties of the chemical elements and their isotopes. Moseley gave the hypothesis that the modern periodic table proposed by Mendeleev depended on the number of protons in the nucleus of a particle. Moseley's hypothesis depended on the study of wavelengths of X-rays that were discharged by chemical elements. It was this hypothesis that established the framework for the atomic number. This article would give you an introduction to atomic number, isotopes, and isobars.
We will learn about the atomic number and mass number, the atomic mass definition, atomic mass formula, atomic weight, and take a look at the atomic mass of all elements.
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Atomic Number
Let us now define the atomic numbers.
The number of protons presents in the nucleus of an atom is known as the atomic number. It is commonly spoken to by Z. It has been set up that the charge of a proton is equal yet opposite to that of an electron. Since a molecule is electrically impartial and neutrons convey no electrical charge, the number of electrons and protons in an unbiased particle is the equivalent. This infers that the atomic number equals the number of electrons or the number of protons in a given molecule. As we realize that elements will in general lose or pick up electrons during numerous chemical reactions, the number of protons is conventionally used to speak to the atomic number of an element. Hydrogen atomic mass number of one as it has just a single proton in its molecule.
Atomic Mass Number
It is the absolute number of protons and neutrons present in the nucleus of an atom. Protons and neutrons present in the nucleus of an atom are together called as nucleons and henceforth the mass number is the number of nucleons present in a molecule. The mass number is spoken to by A. Example: Nitrogen has a mass number of 14 as it has 7 protons and 7 neutrons in its molecule.
Isotopes and Isobars
Those elements that have a similar atomic number yet an alternate mass number are alluded to as isotopes. Isotopes happen because of the presence of an alternate number of neutrons in elements having a similar atomic number as mass number is the aggregate of the number of neutrons and protons. Numerous yet not all elements have isotopes. The isotopes of hydrogen are protium (has one proton and no neutrons), deuterium (has one proton and one neutron) and tritium (has one proton and two neutrons). The chemical properties of isotopes are similarly inferable from the way that they have a similar number of protons and subsequently the similar number of electrons which decides the chemical properties of an element.
Isobars, then again, are the atoms having a similar mass number however an alternate atomic number. For example, the atomic mass of carbon and nitrogen is 6 and 7 individually. Carbon-14, which is an isotope of carbon, has an atomic mass number 14, the same as nitrogen and henceforth both carbon-14 and nitrogen are isobars.
FAQs on An Introduction to Atomic Number, Isotopes and Isobars
1. What is an atomic number (Z) and what does it signify about an element?
The atomic number (Z) represents the number of protons found in the nucleus of an atom. It is the fundamental characteristic that uniquely defines a chemical element and its position on the periodic table. Since a neutral atom has an equal number of protons and electrons, the atomic number also indicates the number of electrons.
2. How is the mass number (A) of an atom determined?
The mass number (A) is the total count of protons and neutrons (collectively called nucleons) in an atom's nucleus. It is calculated using the formula: A = (Number of Protons) + (Number of Neutrons). For example, a carbon atom with 6 protons and 6 neutrons has a mass number of 12.
3. What is the main difference between isotopes and isobars?
The primary difference lies in what property they share. While both relate to atomic structure, they are defined by different parameters:
- Isotopes are atoms of the same element. They have the same atomic number (same number of protons) but a different mass number (different number of neutrons).
- Isobars are atoms of different elements. They have a different atomic number (different number of protons) but share the same mass number.
4. Why do different isotopes of the same element share identical chemical properties?
The chemical properties of an element are determined almost entirely by its electron configuration, specifically the number of valence electrons which participate in chemical bonding. Since all isotopes of an element have the same number of protons, they must have the same number of electrons to remain electrically neutral. This identical electron structure causes them to behave and react chemically in the same way.
5. If isobars have the same mass number, why are they considered completely different elements?
An element's identity is defined exclusively by its atomic number (the number of protons), not its mass. For example, Argon-40 (18 protons) and Calcium-40 (20 protons) are isobars because they both have a mass number of 40. However, because they have different numbers of protons, they also have different numbers of electrons. This results in distinct electron configurations, making them unique elements with completely different chemical properties.
6. Can you provide a few common examples of isotopes and isobars?
Certainly. Here are some common examples that illustrate the concepts:
- Examples of Isotopes: The element hydrogen has three well-known isotopes: Protium (1 proton, 0 neutrons), Deuterium (1 proton, 1 neutron), and Tritium (1 proton, 2 neutrons).
- Examples of Isobars: Carbon-14 (6 protons, 8 neutrons) and Nitrogen-14 (7 protons, 7 neutrons) are isobars. Both have a mass number of 14 but are different elements.
7. What are some important real-world applications of isotopes?
Isotopes have numerous vital applications across science, medicine, and industry. Key examples include:
- Carbon-14: Used in radiocarbon dating to determine the age of ancient organic materials and fossils.
- Cobalt-60: A source of gamma rays used in radiotherapy to treat cancer by targeting malignant cells.
- Uranium-235: A key fuel for nuclear power plants, used to generate electricity through nuclear fission.
8. Why is an element's atomic mass on the periodic table often a decimal, while the mass number is always a whole number?
This is a crucial distinction. The mass number is a count of particles (protons + neutrons) in a single, specific atom (isotope), so it's always an integer. The atomic mass shown on the periodic table is a weighted average of the masses of all naturally occurring isotopes of that element, based on their relative abundance. Because most elements exist as a mixture of several isotopes, this calculated average is typically a decimal value.
