Question

which characteristic of an element determines its placement in the periodic table?
a size
b number of protons
c number of neutrons
d mass

Explanation:

The periodic table is arranged based on the atomic number of elements. The atomic number is equal to the number of protons in an atom of an element. Each element has a unique number of protons, which determines its position in the periodic table. Size, number of neutrons, and mass do not determine the placement in the periodic table in the fundamental way that the number of protons (atomic number) does.

Answer:

B. number of protons