Question

what is the method for organizing elements in the periodic table?

only the atomic number of an element

only the atomic mass of an element

Explanation:

The modern periodic table organizes elements by atomic number (the number of protons in an atom's nucleus). Earlier attempts used atomic mass, but modern organization is based on atomic number, as it better reflects chemical properties and periodic trends. The option "only the atomic mass" is incorrect as atomic mass was used in older versions but not the modern method, and the correct organizing principle is atomic number.

Answer:

A. only the atomic number of an element