The atomic number tells us how many __ or __ an element contains.

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Electrons or Protons

Explanation:-
Atomic number (Z) is defined as:
>>“The total number of protons in the nucleus of an atom is called atomic number”. All atoms of an element have the same number of protons and electrons.
>>“The total number of protons in the nucleus or electrons revolving around the nucleus of an atom”.
Example:
For instance, Hydrogen has the Atomic number(Z) 1.
Helium has the atomic number 2.
Oxygen has the atomic number 8.
| Note | Atomic number is represented by “Z”. And some ppl don’t consider the 2nd definition it’s upto u to do both or the standard one.

Hello thereone of the following properties was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version. which property fits this description? answer: atomic mass  was originally used to arrange elements on the periodic table, but is no longer used to organize the modern version.

Contained in chromosomes which are located in the nucleus of the cell.