21. The order of elements in the modern Periodic Table is based on elements C. chemical symbol A atomic number D. Atomic mass B B name of element​

Sagot :

Answer:

atomic number

Explanation:

the elements in the modern periodic table is based on increasing atomic number which is the number of protons in the nucleus of an atom. as you can notice, the periodic table starts with the element Hyrodrogen which has 1 atomic number, followed by helium which has 2 atomic number, and so on and so forth.