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Strictly, Atomic Mass is not organised on the Periodic Table - the periodic table is arranged according to the atomic number (i.e. the number of protons in the nucleus) of the elements.

However, as the number of neutrons that are required in the nucleus increases as the number of protons increases, it means that with increasing atomic number you generally get a increase in atomic mass as you go further up the periodic table.

BUT, there are exceptions - for complex reasons relating to nuclear stability, the average atomic mass of cobalt (atomic number 27) is actually greater than that of nickel (atomic number 28), and the atomic mass of plutonium (atomic number 94) is greater than that of Americium (atomic number 95).

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11y ago

The periodic table is arranged by atomic number. It has never been arranged by mass number. It was once arranged by mean atomic mass but that had inconsistencies, because for example potassium is lighter than argon.

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Q: How was mass number arranged in the periodic table?
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Related questions

How were the elements in the periodic table arranged?

By Atomic Mass


How is the periodic table is organized into columns called?

The elements arranged according to their atomic number in the table are called periodic table.


Is the periodic table of elements arranged in increasing mass?

No. The modern periodic table is arranged in accordance to increasing atomic number and repeating properties.


Mendeleev arranged the elements in his periodic table in order of?

Mendeleev arranged the elements in his periodic table in order of increasing atomic mass while also grouping elements with similar properties together. His periodic table laid the foundation for the modern periodic table we use today.


What does the atomic number and atomic mass have to do with the arrangement of the elements on the periodic table?

The elements on the periodic table are arranged in order of increasing atomic number.


How was moseleys periodic table arranged?

Compared to Mendeleev's periodic table which was arranged my atomic mass, Moseley's was, however, arranged by atomic number.


How is the periodic table used to arrange the elements?

The periodic table used to be arranged by increasing atomic mass. Now, it is arranged by increasing atomic number (number of protons in an atom of element).


Who developed periodic table?

Niels Bohr: the modern periodic table where the elements are arranged in the increasing order of atomic number Mendeleev: The periodic table where the elements are arranged in the increasing order of atomic mass


Is your modern periodic table based on atomic mass or atomic number?

The modern periodic table is arranged according to the elements' atomic numbers.


How did he arrange similar elements on the periodic table?

In Mendeleev's periodic table the elements are arranged in increasing atomic mass and repeating properties whereas in in the modern periodic table the elements are arranged in increasing atomic number and repeating properties.


Who is the scientist who recognized the periodic table for atomic number?

The scientist who recognized the periodic table for atomic number was Henry Moseley. He discovered that elements should be ordered by atomic number rather than atomic mass, which led to the modern understanding of the periodic table.


Are the elements on a periodic table arranged in order of decreasing atomic mass?

No. The elements are arranged in order of increasing atomic number.