Question

the modern periodic table is arranged in order of increasing atomic ____. mass charge number radius

Explanation:

The modern periodic table arranges elements by atomic number. Atomic number is the number of protons in an atom's nucleus. This arrangement helps in understanding element properties and trends. Mass (atomic mass) was used in earlier tables but has inconsistencies. Charge (not a standard term for this arrangement) and radius (a property that varies periodically but not the basis of arrangement) are incorrect.

Answer:

C. number