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Difference Between Atomic Mass and Atomic Number

Main Difference

The main difference between Atomic Mass and Atomic Number is that Atomic Mass is the total number of neutrons and protons in the nucleus of an atom, whereas Atomic Number is the total number of protons existing in the nucleus of an atom.

Atomic Mass vs. Atomic Number

The total number of neutrons and protons that exist in the nucleus of an atom combine to make the mass of the atom known as its atomic mass. So, atomic mass is the average weight of an atom. On the flip side, the total protons numbers that are present in the atom’s nucleus known as the atomic number.

The atomic mass is also recognized as atomic weight whereas, and the atomic mass is also recognized as a proton number. The atomic mass is denoted by the letter ‘A.’ On the other hand, the atomic number denoted by the letter ‘Z.’ Atomic mass not used to differentiate between different elements. On the flip side, the atomic number used for the identification and classification of different elements. The atomic mass of an element can measure by using an atomic mass unit (amu). On the flip side, an atomic number is a number or a digit that can use to fix elements in a periodic table.

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As the isotopes of an atom have the same number of protons but the different number of neutrons so, atomic mass can be used for the classification of different isotopes of an element. On the other side, all the isotopes of an element have the same atomic number so, it cannot use to classify them. For example, the atomic mass of carbon is twelve and thirteen for its two isotopes. On the flip side, its atomic number is six for all isotopes.

Comparison Chart

Atomic MassAtomic Number
The total number of neutrons and protons existing in the nucleus that form the mass of an atom is known as atomic mass.The total protons number existing in the atom’s nucleus is called the atomic number.
Also Known As
It also recognized as atomic weight.It also recognized as a proton number.
Representation
It represented as the average weight of an atom.It represents the number of nucleons, i.e., protons in the nucleus.
Denoted As
The letter ‘ A denotes the atomic mass.’The atomic number symbolized by the letter ‘Z.’
Isotopes
Isotopes of an atom have different atomic mass.Isotopes of an atom possess the same atomic number.
Identification of Isotopes
Atomic mass helps in the identification of different isotopes.It cannot use to identify the different isotopes of an atom.
Classification of Elements
Atomic mass is not used to differentiate between different elements.The atomic number is used for the identification and classification of different elements.
Calculations
The atomic mass of an element can measure by using an atomic mass unit (amu).It is a number or a digit that can use to fix elements in a periodic table.
Relation
It can find out by adding the number of neutron in the atomic number.It can find out by deducting the number of neutron from the atomic mass of an element.
Example
The atomic mass of carbon is twelve and thirteen for its two isotopes.The atomic number of carbon atom is six for all isotopes.
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What is Atomic Mass?

Atomic mass is represented as the average weight of an atom and also recognized as atomic weight. An atom is composed of three subatomic particles, i.e., protons, neutrons, and electrons, as electrons are very light in weight, so the atomic mass considered as the mass of a total number of neutrons and protons present in the nucleus of an atom.

The letter ‘ A denotes the atomic mass.’ It expressed in the form of a unified atomic mass unit or ‘amu.’ One atomic mass unit is equal to 1/12 of the mass of a single C12 or carbon-12 atom with a value of 1.660 539 066 60(50) × 10−27 kg. For example, the mass of a carbon-12 atom equaled to12 amu. As electrons are very light in weight, so, the mass of a carbon-12 isotope is composed of 6 neutrons and 6 protons. The protons and neutrons have the same mass so, it said that they both have a mass equal to 1 u.

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As different isotopes of an atom vary in the number of neutrons. So, they all have different atomic mass. That is why atomic mass can use to identify different isotopes of an element. But, it is not used to differentiate between different elements. The atomic mass of an element can also find out by adding the number of the neutron in its atomic number.

What is the Atomic Number?

The atomic number is the total number of protons present in the nucleus of an atom. It also recognized as a proton number. It denoted by the letter ‘Z.’ As all the isotopes of an element have the same proton number so the atomic number cannot use to differentiate between the isotopes of that element.

The atomic number is used for the identification and classification of different elements. It is a number or a digit that can use to fix elements in a periodic table. Different elements are identified according to their specific atomic number and placed in the periodic table according to it.

For example, an atom that has atomic number 12 is carbon as it has 12 protons in its nucleus. An atom with different atomic numbers will be a different number. In the periodic table, all the elements arranged according to their increasing atomic number. So, the top most element present at the upper left corner of the table is hydrogen with atomic number 1. The next one is helium with atomic number 2 and so on.

As atomic mass is the number of protons and neutrons in the nucleus of an atom so, the atomic number can also find out by deducting the number of the neutron from the atomic mass of an element.

Key Differences

  1. The total number of neutrons and protons existing in the nucleus of an atom is known as atomic mass whereas, the total number of protons present in the nucleus of an atom is known as the atomic number.
  2. The atomic mass also recognized as atomic weight. On the flip side, the atomic number also recognized as a proton number.
  3. The atomic mass represented as the average weight of an atom. On the other hand, the atomic number represents the total number of nucleon, i.e., protons in the nucleus.
  4. The atomic mass is denoted by the letter ‘A.’ Conversely, the atomic number is denoted by the letter ‘Z.’
  5. Isotopes of an atom have different atomic mass. On the flip side, the isotopes of an atom showing the same atomic number.
  6. Atomic mass helps in the identification of different isotopes. On the other side, the atomic number cannot use to identify the different isotopes of an atom.
  7. Atomic mass not used to differentiate between different elements, while the atomic number used for the identification and classification of different elements.
  8. The atomic mass of an element can be measured by using an atomic mass unit (amu). On the other hand, an atomic number is a number or a digit that can use to fix elements in a periodic table.
  9. The atomic mass of an element can find out by adding the number of the neutron in its atomic number, whereas; the atomic number can find out by deducting the number of the neutron from the atomic mass of an element.
  10. The atomic mass of carbon is twelve and thirteen for its two isotopes. On the flip side, the atomic number of carbon atom is six for all isotopes.

Comparison Video

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Conclusion

The above discussion summarizes that atomic mass is the average weight of an element that is equal to the number of its protons and neutrons in the nucleus. On the other side, the atomic number is the protons number present in the atom’s nucleus.

Harlon Moss

Harlon currently works as a quality moderator and content writer for Difference Wiki. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss