Question

No two elements will have the same ________ ___________


atomic number


mass number

Answer 1

No two elements will have the same **atomic number**. The atomic number is defined as the number of protons in the nucleus of an atom, and it uniquely identifies each element on the periodic table. In contrast, mass number, which is the total number of protons and neutrons in an atom, can be the same for different isotopes of an element or even for different elements.