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Isotopes vs. Isobars: What's the Difference?

Edited by Janet White || By Harlon Moss || Updated on October 25, 2023
Isotopes are atoms of the same element with different neutron counts, while isobars have different elements but the same atomic mass.

Key Differences

Isotopes and isobars are terms that refer to atomic structures, but they are defined by different characteristics. Isotopes concern elements that have the same number of protons but varying numbers of neutrons. For instance, carbon-12 and carbon-14 are both isotopes of carbon, as they share the same atomic number but have different neutron counts, leading to different atomic masses.
Isobars, conversely, relate to atoms from different elements that share the same atomic mass but have different atomic numbers. This means they have different numbers of protons. An example would be argon-40 and calcium-40, which both have an atomic mass of 40 but differ in atomic numbers. These two atoms are isobars.
Understanding the distinction between isotopes and isobars helps clarify concepts in nuclear physics and chemistry. While isotopes are chemically alike because they belong to the same element, they can possess different physical properties due to their varied masses. On the other hand, isobars, being from different elements, have diverse chemical properties.
The importance of isotopes lies in various applications ranging from medical imaging to dating ancient artifacts. Isobars don't generally have the same widespread applications, but the term is crucial for understanding atomic structures and the distribution of elements on the periodic table.
To encapsulate, while isotopes and isobars both revolve around atomic structures, isotopes concern the neutron variation in atoms of the same element, and isobars relate to atoms from distinct elements with the same atomic mass.

Comparison Chart


Atoms of the same element with differing neutron counts.
Atoms of different elements with identical atomic masses.

Atomic Number


Atomic Mass

Can vary

Chemical Properties



Carbon-12 and Carbon-14
Argon-40 and Calcium-40

Isotopes and Isobars Definitions


Atoms with identical atomic numbers but different atomic masses.
Uranium-235 and Uranium-238 are isotopes used in nuclear reactors.


Atoms with the same atomic mass but different elements.
Argon-40 and Calcium-40 are isobars with an atomic mass of 40.


Atoms of the same element with varied neutron counts.
Carbon-12 and Carbon-14 are isotopes of carbon.


Atoms with differing atomic numbers but the same mass number.
Isobars can be found across the periodic table but share a mass number.


Share the same number of protons but have varied neutrons.
The varying number of neutrons differentiates isotopes from each other.


Possess different chemical properties.
Isobars, being of different elements, react differently in chemical reactions.


Chemically alike but may differ physically.
Isotopes of an element generally have similar chemical reactivity.


Have different numbers of protons and neutrons.
Isobars differ in their proton-neutron composition, leading to varied atomic numbers.


Used in diverse applications, from medicine to archaeology.
Radiocarbon dating uses isotopes to determine the age of ancient artifacts.


Atomic structures with the same weight but distinct identities.
Despite having the same atomic weight, isobars are distinct elements.


One of two or more atoms having the same atomic number but different mass numbers.


A line on a weather map connecting points of equal atmospheric pressure. Also called isopiestic.


Plural of isotope


Any of two or more kinds of atoms having the same atomic mass but different atomic numbers.


Plural of isobar


Are isotopes and isobars the same?

No, isotopes are atoms of the same element with different neutron counts, while isobars are atoms of different elements with the same atomic mass.

Can isotopes have different atomic masses?

Yes, isotopes of the same element can have different atomic masses due to varying neutron counts.

Are the chemical properties of isobars similar?

No, isobars have different chemical properties as they are different elements.

How can one identify isotopes?

Isotopes of an element have the same atomic number but different atomic masses.

How are the neutron counts of isotopes and isobars determined?

Subtracting the atomic number from the atomic mass gives the neutron count.

Can the number of electrons differ in isotopes?

No, isotopes of an element have the same number of electrons.

Do isobars have the same neutron count?

Not necessarily. Isobars can have different neutron counts despite having the same atomic mass.

Why is it important to differentiate between isotopes and isobars in studies?

Differentiating helps understand atomic structures, nuclear behavior, and chemical properties of elements.

Which isotope is commonly used in dating ancient artifacts?

Carbon-14 is widely used in radiocarbon dating.

Can isobars be found in the same spot on the periodic table?

No, isobars belong to different elements and hence occupy different positions on the periodic table.

Are the physical properties of isotopes identical?

Not always. Isotopes can have different physical properties due to their varied masses.

How do isobars differ from isotones?

Isobars have the same atomic mass, while isotones have the same number of neutrons.

Why are some isotopes radioactive?

Some isotopes are unstable and release radiation to achieve stability.

What is a practical application of isotopes?

Isotopes are used in medical imaging, radiocarbon dating, and nuclear energy.

Do isobars have the same number of protons?

No, isobars have different numbers of protons, which gives them different atomic numbers.

Why don't isobars have the same chemical properties?

Isobars are atoms of different elements, and thus their chemical behaviors differ.

What makes isotopes chemically alike?

Isotopes have the same number of protons and electrons, leading to similar chemical properties.

Can isobars be isotopes of different elements?

No, isobars are never isotopes as they always represent different elements.

Which has more application in daily life, isotopes or isobars?

Isotopes have more practical applications, including in medicine, agriculture, and archaeology.

Why are isotopes significant in nuclear reactions?

Certain isotopes, like Uranium-235, can undergo fission, releasing energy in nuclear reactors.
About Author
Written by
Harlon Moss
Harlon is a seasoned quality moderator and accomplished content writer for Difference Wiki. An alumnus of the prestigious University of California, he earned his degree in Computer Science. Leveraging his academic background, Harlon brings a meticulous and informed perspective to his work, ensuring content accuracy and excellence.
Edited by
Janet White
Janet White has been an esteemed writer and blogger for Difference Wiki. Holding a Master's degree in Science and Medical Journalism from the prestigious Boston University, she has consistently demonstrated her expertise and passion for her field. When she's not immersed in her work, Janet relishes her time exercising, delving into a good book, and cherishing moments with friends and family.

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